What does 'Adult' work in the modeling industry mean?

'Adult' means that the type of picture you'll be expected to do are the type of pictures that appear in top shelf magazines like, Penthouse, Mayfair and Escort.
The kind of images you'd typically have to pose for involve nude, open leg shots and the like.

Important Note:
Assume that everyone you know will see your pictures on the internet!
Although it is unlikely to happen what with the millions of websites out there you must face the fact that it might happen, so only do adult work if you don't mind your friends, family and work colleagues seeing your pictures, and no, you can’t get away with not showing your face, however great the rest of you is.