They're a short decription (abbreviation) to how the original video file was sourced or converted. cam means it was captured with a vid-camera ... possibly from a theatre. dvd rip means it's been taken directly from a dvd release & had the securities subtracted from it before converting to another format. The larger these ones are the better they are. If they are split into parts then all the better; Movie download issues

Others will fill you in on the rest.