college: College porn is a genre that focus on students. It features young performers an a college lifestyle: dorms, frats, sororities...
gay: HOMOSEXUAL. Refers to both homosexual men and homosexual women (also called LESBIANS).
hardcore: Explicit movies or videos that show genitals, especially an erect penis, and often include penetration. In this meaning, "hardcore" is the exact opposite of SOFTCORE. But for many porn videos, it just means an intense or dangerous sexual activity.