Most anime terms have simple descriptions, but "moe" is a complicated topic since it's similar to many things, but it's also a new concept itself. I settled on a super short explanation of "affection for a character attribute" on some pages, but that's a lot like describing WWII as "a bunch of people died". It's a term that's thrown around a lot, but few people ever bother to explain it. So what is moe anyway?
Moe (pronounced mō-eh) is a more recent development in anime culture. The first kanji (萌) means budding or sprouting. Moe coincidentally is also how you pronounce "burning" in Japanese, which is occasionally used as a pun, but feeling a fiery passion towards characters is pretty descriptive too.
Take a broad concept such as "romance" for example. This can be further refined to a certain type of film people like, further refined to a few particular characters, and finally down to a few specific attributes about those characters that made them likable. This is what happened in the anime industry. After years of producing anime titles, animation studios took note of peoples tastes, which is particularly easy with such a fanatical fan base like anime fans. Especially with common character popularity polls. Cross referencing what is popular only makes sense for anime studios.
It might seem melodramatic to say even one title changed the landscape of anime, never mind a single character; but Rei changed the game as to what an anime character could be. It's almost counter intuitive that she would become so rabidly popular. You can describe the show, her actions, or what happens to her, but describing her as a character is difficult as her defining defining feature is an absence of personality. She's quiet, and aloof but doesn't seem to have any background as to why she's that way. Rei reached a height of popularity never seen before in the anime industry. Not surprisingly, anime became overwhelmed by "Rei clones" which are very doll like. The changes didn't stop with simply emulating Rei. It also changed the thinking as to what anime fans want in a character, and why.
The adage "sex sells" is well known, but other human emotions have entire genre's based off them too. For example, horror is based off of fear. Anime had stumbled on something previously untapped: the human paternal/maternal instinct to nurture. If sex sells, fear sells... then perhaps nurturing can also sell. Moe is a response to a kind of character: not a thing, but something which causes that response.
This nurturing instinct can create an instant bond to a character, simply by having that character exhibit certain features that bring out that instinct. While most previous anime titles involving romance had focused on a love which inevitably was somewhat sexual in nature, moe presents a different kind of "pure love" like that seen between parent and child. This isn't merely a parent/child phenomenon though. Often people also feel the need to nurture/console their friends, family and lovers. A moe character is one who has defining traits (possibly lacking any other traits/personality at all) to invoke this emotion in the viewer. It's like a character being "adorable" and inspiring adoration in an audience. While adoration is the most common attribute, moe can gain appeal in other ways too, although I'm not a very good person to clarify such a vague topic.
Another key factor is that moe is fantasy. This seems obvious being anime, but anime characters can be developed in a way that is just as real as those in a book or movie. Moe moves beyond this in a way that is idealized, and makes little to no attempt in being realistic. That's a big factor as to why moe is an anime/manga phenomenon.
By this point I (hopefully) described moe well enough, while giving you absolutely no idea what actually qualifies as a moe character. Moe isn't restricted to a character's personality. It can also exist through occupations and even situations. This isn't an all encompassing list, but should give you a good idea of what can qualify as moe. Descriptions are more of a personal interpretation. As moe deals with a vague sense of human emotion, it is anything but an exact science. Two people can find a character moe, but for different reasons. It depends on the person. It also provides me a good chance to elaborate on some anime terms that are relevant and I couldn't figure out where else to talk about them on my website -_-;
The little sister (imouto) type doesn't seem intuitively moe until you think about the relationship two siblings can have. A young sister doesn't automatically qualify as moe, it's depends on how the relationship is presented. A moe style little sister is cute, and projects a sense of innocence. Her relationship with her older brother is one of affection, and adoration. She may also display signs of jealousy when other girls take an interest in him. The little sister plays on the desire for a family environment, the desire to nurture, and also the feeling of being adored. This is of course idealized, as anime characters are no where near as annoying as real little sisters, and have the added benefit of being able to turn off the TV when you don't want to deal with them.
The childhood friend is an example of "a situation for moe". When two children become friends, their relationship is innocent. Children aren't motivated by greed or lust, but instead form a bond that is genuine. One avenue taken by anime, is that this friendship continues throughout the years, and the childhood friend becomes like a sister. Neither has a romantic interest in the other, but their friendship is still founded on that initial relationship. The other avenue is the latent crush that develops. Despite evolving into a romantic interest, the relationship maintains a level of purity because it was founded on the childhood friendship. This can be further idealized if the two are separated for a period of time. Even when apart, the girl harbors those feelings for her love through all those years, and her heart never wavers.
The childhood friend also offers a plot convenience in anime. Instead of two people meeting, getting to know each other, and possibly falling in love, this is written off as "the two are childhood friends".
The term tsundere comes from "tsun-tsun" (cold/harsh) and "dere-dere" (lovey-dovey). When combined it means a type of character which is normally cold, but has a tender side that shows through. This kind of character has become so pervasive throughout anime that it's almost rare to not have at least one character in a title that qualifies. Tsundere characters have many variations, so while they are popular, they are more resistant to becoming as tired as other moe types. They're also good at creating drama, comedy, and romance all wrapped up into one package.
The tsundere evolved from early date sim games, where there was often one girl who was colder than the rest and took considerably more effort to win over. The tsundere inspired moe probably comes from a sense of vulnerability a person can have. This character may need support, or fulfillment that they have yet to experience.
The most common form of tsundere is the cold attitude character, who eventually shows signs of being in love. She's generally abusive, berates her love interest verbally, and possibly goes out of her way to simply make him miserable. Her tender side may accidentally show and she's probably embarrassed about it. Tell tale signs include blushing, stammering words, denying acts of kindness or sudden outbursts to cover up her lapse in cold personality.
A second variation is the other side of the coin, where a tsundere is normally a kind loving person, but has outbursts of violence and/or abusive language. This is often triggered by jealousy, but can also emerge from faults in her love interest (being stupid, a pervert, etc).
Aside from those two extremes anything in the middle may also qualify, such as a character with extreme mood swings.
One of the more fascinating moe types is the yandere. The term comes from combining yanderu (mental illness) and dere-dere (lovey dovey). This is a type of character who is sweet and loving, but to the point of becoming obsessive and so dedicated that she's considered crazy. Yes, only in Japan would being psycho be considered an endearing attribute. The yandere offers purity through her dedication. Her heart is unwavering to the point where she's willing to cast off sane constraints to keep her love. This also creates a sense of nurturing in that this kind of character is simply misguided, but has a good heart.
By now you can probably see a common theme forming with the "dere-dere" line of characters. This includes character types such as dandere - normally emotionless but can show a loving side, like coming out of her shell, or the less common term kuudere cold exterior, warm inside - different from tsundere in that the mood swing is much less intense, and the loving side rarely shown.
Similar to childhood friend which offers moe by a situation, the maid can provide moe through a profession. The relationship between a maid and her master is one of virtue and dedication. The maid does her best to please her master, and he in turn feels the need to provide for her and appreciation for her service. This isn't to say that maids are always moe, but they can end up that way. An important part of moe is the cute factor, and the maid costume is very conductive to that end. Nurses work in a similar way, and not surprisingly are also costume oriented. From a female perspective, a prince can also offer this sense of dedication and service, with a sense of chivalry towards a woman. Maids also offer considerable fetish material, so pretty much everyone agrees there is something appealing about them. Which is probably why they've become rabidly popular in Japan.
Maid moe has a lot to do with the outfit, but other external characteristics can make a character much more adorable and inspire moe too. Cat ears, having a tail, and even some more mundane things like glasses can all be considered moe traits.
Some of these things can also be combined to form mega-moe. Like the Tsundere Childhood-Friend Maid.
The good, the bad and the ugly
Moe's involvement with sexuality is probably an inevitable topic. Moe by it's nature doesn't have much to do with sex - nearly the opposite. This doesn't mean that element doesn't exist. Sex is an instinct ingrained into human beings. Making characters of the opposite sex that are attractive by design, and having existing affection towards them (through moe) can give moe a sexual basis too. This is not necessarily a bad thing either, as nurturing emotions are often shared between lovers in a deep relationship. Moe however is not necessarily used with this intent. A maid outfit for example can be sexy, or simply cute. Her personality can also be sexy or moe. Keep in mind that there is a gray area between moe and other sexually oriented genres such as lolicon (lolita complex) in anime/manga.
I've typically used "she" to denote the moe character, and "he" to refer to the anime fan, but (otaku) girls are into moe as much as the guys. Girls manga/anime genre called Boy Love (aka yaoi) has become a focal point in moe for girls. Why this requires a homosexual relationship is something I still don't understand, but in Japan I guess this relationship is considered "less dirty". Moe does offer an appeal to girls in regular anime as well. Because moe isn't an attraction in the romantic sense, and operates on a level of being adorable, female moe characters may be more appealing to girls.
What does this mean for anime? Moe is a natural evolution in a market where the producers (anime studios) are in touch with their fan base (otaku), and both have grown together, so the development of moe was probably inevitable (also considering some social factors). Adapting to the desires of their fan base, studios are able to better create characters which are popular and likable. There are of problems with moe too however.
Moe has become popular in anime not only because it's so well liked, but also because it sells. Commercialism turning moe into a product has potentially severe consequences the anime industry is already starting to feel. As moe is popular, many series incorporate it and anime has become more and more dependent on moe. When done correctly, moe becomes a feature of a title. Instead it's becoming common for moe to be used as a shortcut, where characters are simply drawn forth by a random assortment of popular archetypes and grafted into a story with shoddy construction and terrible premise. These however STILL sell. If it takes so much time and effort to produce a good anime series, or why bother when you could paint over the faults with moe? Even if a company puts quality first, competitors may make far more money pumping out garbage obscured by moe. This creates a lot of pressure when budgets are tight.
Anime becoming increasingly insular is another consequence of moe. By pandering to fans with endless references, it becomes harder and harder for anime to gain new fans from the outside. For an outsider, expectations as to what a character should be stems from common types like those found in books and movies. The appeal of moe is not inherently obvious to those new to anime, and this can be a huge turn off. Even for those who are anime fans, moe can induce burnout if they tire of it.
A convenience store might be a good analogy. Think of a store that sells a kind of soda that becomes wildly popular. People come to the store for the soda, and more and more the store increases the shelf space of that soda. People stop thinking of it as a convenience store, and instead it becomes known for that soda. As the store starts to drop other products to increase space for the soda, people stop going there for other things, and this makes the store even MORE dependent on that product. The big question is if the popularity of that drink alone will be enough to support the store. This is the current bind that the anime industry is in. Anime has declined in popularity, advertisement revenue is drying up, but moe still sells. Animation studios are forced to incorporate moe to survive (even if they'd prefer not to), but it's unclear if this is something which can support the industry, or is something causing it to go into a death spiral.
Examples of moe in anime
This is just one of many examples of moe done the wrong way. The concept is shaky to begin with, and there isn't much of a story to talk about. It uses moe archetypes so cut and dried, they feel prefabricated. While still amusing, the show suffers from a severe lack of substance.
One of the main characters is such a textbook tsundere that it's kinda scary, but many other characters qualify as well. Despite using the same formula often used in anime high school titles, Toradora has a very good story and fully develops its characters. Taking the time to do things right and not cutting corners is the key to making this title work. Moe is a feature, not a crutch.
Many titles qualify as moe oriented, but few are as carefully constructed as to be exactly that as Clannad. In fact it's possibly a little too calculated if you specifically look for it. Like it or hate it, Clannad is possibly the most moe thing ever, so if you want an induction into most of what I've mentioned on this page, you'll find a lot of it here.
Yeah yeah, I know. Longest article ever to sum up "a feature which instills a sense of adoration for a character". You may also be thinking that you hear the term moe used for things not meeting the definition here. This page is about the strict meaning of moe, but it's increasingly used people similar to "likability". Since moe is a new word/concept it's probably not correct to say this is misuse of the term, but in the strict sense moe is often used to refer to things which are not moe. Also emerging is the compromise of "moe-ishness", where something can have a degree of moe.