cam: Videos captured by a non-professional camera. This can be a surveillance cam, a webcam, a nanny cam...
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.
homemade: Amateur video donne by the participat(s) with little ressources.