Child pornography is pornography involving children. Production and sale of child pornography is illegal almost everywhere, and many countries also outlaw the mere possession.
Definitions of child porn vary widely. In most countries, "children" are defined to be persons below the age of 14 or 16, and "pornography" is defined to be depiction of actual sexual activity. In these countries, "nudist" magazines with depictions of nude underage persons are widely available. The United States uses a particularly broad definition, which applies to all people appearing to be below the age of 18 and covers all materials aimed at "prurient interests", even if no nudity is involved. Pictures of nude small children in bath tubs have been declared to be child pornography. Recently, the question has arisen of whether materials whose production does not involve actual under-age persons (for instance because computer simulation is used) should also be treated as prohibited child pornography. Proponents of such a prohibition argue that these materials might encourage child molesters, and that the availability of simulated child pornography would make the prosecution of true child pornography much harder. Opponents of the prohibition claim that simulated child porn does not harm children and should therefore be treated as free speech. It is also argued that these materials may give paedophiles a sexual outlet, thereby lowering sexual frustration and the risk of criminal behaviour.
The advent of the internet has facilitated the exchange in child pornography considerably, and several groups engaged in the exchange of child pornography have been uncovered. Typically, participants in these groups do not buy or sell materials, but trade, or post out of a desire to spread them.