Asexuality is defined as not experiencing sexual attraction, and those who identify as asexual are commonly called "ace" within the community. Asexuality is not the same as celibacy as it is not a choice. According to Britain's 1994 National Survey of Sexual Attitudes and Lifestyles, Aces make up around 1% of the population; however, asexuality tends to lack the same amount of visibilty that some other orientations recieve.
Sexual orientation is not linked to gender and anyone of any gender identity can be ace.
The most well-known ace-specific site is AVEN, the Asexual Visibility and Education Network . Resources regarding the orientation as well as a forum are hosted on their website. Asexuals are capable of having any kind of romantic orientation (ie. panromantic, heteroromantic, homoromantic) just like other people, the only difference being that they do not wish to have sex with others no matter what gender they identify as. Some aces do have sex though for a variety of reasons, such as wanting to please their non-ace partner.
2 other sexual orientations are consider part of the asexuality "spectrum": Grey-asexuals and demisexuals. Grey-As occasionally experience sexual attraction, but with far less frequency than other sexual people. Demisexuals on the other hand will only experience sexual attraction to someone if they've already built up an extensive personal relationship with them.
Unlike other sexual orientations, it is less common to use the term asexual as a blanket term for both sexual and romantic preference. This is because for many aces, their sexual and romantic orientation do not line up (ie. not all asexuals are also aromantics). However, people whose romantic and sexual attractions don't match can be found in all orientations.