Porn is sex described or enacted in a way that arouses. There are non-porn sex movies/descriptions for a variety of purposes (usually medical or historical).
Porn is everywhere, you can get it on the net, on TV (even free, when I had Dish there was at least one channel that had very soft porn in the evening), in the library and it's as old as humanity (depictions have been found in Greek, Babylonian, Egyptian, Roman and other 'advanced' cultures as well as cave paintings).
On the net, there are hundreds of free porn sites that offer full or partial videos, pictures of a variety of sources and subjects (also see rule 34). The net gives you the additional benefit of anonymity that you don't have to interact with anyone to obtain it (as you would if you would go to a book store to pick up a magazine).
The internet is destroying the WTBTS (and other cults re: Mormons and Amish) in more ways than one.