verified amateur: As many videos are branded "amateur", which can also mean "low budget professional" lots of sites offer a "certified amateurs" category with only "real" amateurs.
amateur: Like in sports, amateur porn features individuals who are not professional porn stars. It features ordinary individuals partaking in every day sexual acts. Girl/boy next door, wives/husbands, girlfriends/boyfriends. Sometimes real amateurs but quite often professional models just pretending.
big ass: For big booty and massive buttocks lovers.
ass: Video genre that focus on the butts. It can includes anal, asslicking and rimming and even spanking, but also more generic movies that just focuses on asses, big or small.
babe: Usually softcore, this niche features girls that are considered extremely attractive. Beautiful and young female models.