Otherwise known as autoeroticism, autosexuality is referred to as either a sexual experience or a sexual orientation. As a sexual experience or 'autosexual behavior', this practice involves masturbation and sexual fantasies (conscious element), and sexual daydreams (unconscious) even without another person's presence. These autosexual behaviors are being experienced by both autosexuals and non-autosexuals.
For instance, a heterosexual who has a partner can still experience arousal or masturbation just by looking at their naked self in front of a mirror fantasizing that he is having sex with his partner. On the other hand, autosexuality as a sexual orientation refers to being attracted to oneself over a partner due to a troubled sexual response. Autosexuals practice these forms of stimulation because they are sexually aroused by their own bodies and not by external sources such as pornography or other people.
This might sound vain but autosexuality is totally different from narcissism. One thing that makes the two different is on how autosexuals and narcissists carry themselves in a crowd. While narcissists will want to impress other people by the way they look or by their manner of dressing, autosexuals do not care about others' compliments because they are attracted to and satisfied with their own bodies.