The pleasure of sex arises from factors including the release of neurochemicals such as oxytocin and dopamine, and the sense of connection expressed through touching, massaging, and cuddling.
There is no one way to be sexual, and there is enormous variation in the activities that people find arousing. Men are especially stimulated by visual imagery: About 90 percent of young men report using pornography with some regularity. Many couples today engage in behaviors that were once perceived as atypical, including dominance play and anal intercourse. Researchers now understand that flexibility in sexual repertoires is healthy and generally enhances relationships. Clinicians regard specific behaviors as problematic only when they create harm or distress for one or both partners or when the behavior is compulsive—that is, it becomes the only means of arousal.
"Sex addiction" is a label often used to suggest an excessive or pathological interest in sex, but studies show that this perception is more tied to one's moral or religious outlook than to actual sexual practice.
To learn more see Arousal, Orgasm and Post-Coital Behavior and Hookups and Casual Sex.