Topic summary
Sex act

Extracted from the Wikipedia article Human sexual activity.
Types
Sexual activity can be classified in a number of ways. The practices may be preceded by or consist solely of foreplay. Acts involving one person (autoeroticism) may include sexual fantasy or masturbation. If two people are involved, they may engage in vaginal sex, anal sex, oral sex or manual sex. Penetrative sex between two people may be described as sexual intercourse, but definitions vary. If there are more than two participants in a sex act, it may be referred to as group sex. Autoerotic sexual activity can involve use of dildos, vibrators, butt plugs, and other sex toys, though these devices can also be used with a partner.