Still or moving images, usually of women, in varying states of nudity, posing or performing erotic acts with men, women, animals, machines, or other props. Some say it degrades women, some say it corrupts young boys (who down-load it from the {WorldWideWeb} or exchange it on {FloppyDisks}). Most of it is in the form of {JPEG} images. There are many sites on the {World-Wide Web} offering porn of all sorts, almost always for a Subscription. It is said that these are a driving force in the Evolution of new Technology and techniques for the web. Advertisements for them certainly constitute a significant proportion of all {spam}. There are even pornographic ComputerGames, an early example being {Mac Playmate}.
Beware - many institutions, particularly universities, have strict rules against their computers and networks being used to transfer or store such things, and you might get corrupted.