Friends with benefits is where two people have sex with someone they generally consider a friend or someone they are fairly close to.
During the sexual revolution in the United States and Europe in the 1960s and 1970s, social attitudes to sexual issues underwent considerable changes.
Recreational or social sex refer to sexual activities that focus on sexual pleasure without a romantic emotional aspect or commitment.
Recreational sex can take place in a number of contexts: for example, in an open marriage, A hookup (colloquial American English) is a casual sexual encounter involving physical pleasure without necessarily including emotional bonding or long-term commitment; it can range from kissing (for example, making out) to other sexual activities.
A one-night stand is a single sexual encounter between individuals, where at least one of the parties has no immediate intention or expectation of establishing a longer-term sexual or romantic relationship.
Anonymous sex is a form of one-night stand or casual sex between people who have very little or no history with each other, often engaging in sexual activity on the same day of their meeting and usually never seeing each other again afterwards.