Asexuality is generally defined as a lack of sexual attraction to anyone of any gender, however, some people who experience sexual attraction but don’t have any desire to act on it also identify as asexual. Asexual people generally do not want to and do not have sex, however some do for different reasons. Most asexual people still experience romantic attraction and get crushes on people and fall in love. They often identify with a separate romantic orientation label, such as heteroromantic, homoromantic, biromantic or aromantic. The different between being asexual and sexual is not black and white, and some people feel they fit somewhere between the two and identity as grey asexual. Asexuality is different from celibacy in that most celibate people still experience sexual attraction and sexual desire, they just choose not to act on it, often for religious reasons.
Sexual attraction is one reason that asexual people have sex. Some other reasons beyond sexual attraction that asexual people and sexual people have sex are:
- Their partner is sexual and they are willing to engage in it to please their partner (this only counts as sex rather than rape if they are not pressured)
- Some asexual people enjoy the physical and emotional intimacy that comes with sex
- Some asexual people still have a sex drive and masturbate and orgasm. So some of them like to have sex for the sexual pleasure it provides, in a similar way to the way some heterosexual women, for example, like to have sex with women, but don't consider themselves sexually attracted to women. Sexual orientation is generally defined as internal feelings, rather than external behaviour.
It's important to note that these are all reasons that people have sex on top of sexual attraction, but sometimes they have sex for the reasons above without sexual attraction, whether they're asexual or not.
Some links for more information:
A nice cartoon explaining what asexuality is and some myths that surround it can be found here.