Porn or not, representations of sexual behavior have existed through the centuries and across cultures. It has been said that pornography documents man's archetypical concern with sexuality. But does this mean that the reasons for its existence, or the functions of porn, have remained the same over time? The answer is no.

Before we can answer the question of why people use porn, we need to ask what porn is, and who its users are. Although lawyers, feminists, priests, and scientists all have tried to describe it, a satisfactory definition of porn does not exist. Some distinguish between erotica and porn, with porn being more violent, portraying unequal power in sexual relations, or showing activities that are judged to be immoral. The Webster dictionary defines pornography more instrumentally, through one of its presumed functions, as "the depiction of erotic behavior intended to cause sexual excitement."