In some cultures, sexual activity is considered acceptable only within marriage, while premarital and extramarital sex are taboo.
Some sexual activities are illegal either universally or in some countries or subnational jurisdictions, while some are considered contrary to the norms of certain societies or cultures.
These include erotic asphyxiation and self-bondage. The potential for injury or even death that exists while engaging in the partnered versions of these fetishes (choking and bondage, respectively) becomes drastically increased in the autoerotic case due to the isolation and lack of assistance in the event of a problem.
Sexual activity can be consensual, which means that both or all participants agree to take part and are of the age that they can consent, or it may take place under force or duress, which is often called sexual assault or rape.
From a biochemical perspective, sex causes the release of endorphins and increases levels of white blood cells that actually boost the immune system.
If there are more than two participants in the sex act, it may be referred to as group sex.
Autoerotic sexual activity can involve use of dildos, vibrators, anal beads, and other sex toys, though these devices can also be used with a partner.
Sexual arousal can also be experienced from foreplay and flirting, and from fetish or BDSM activities, or other erotic activities.
Most commonly, people engage in sexual activity because of the sexual desire generated by a person to whom they feel sexual attraction; but they may engage in sexual activity for the physical satisfaction they achieve in the absence of attraction for another, as in the case of casual or social sex.