APS (Advanced Photo System) film was a format introduced by Kodak and copied by everyone else It was a replacement for the Instamatic formats first introduced in the mid-1960's. These formats all had in common that the film was in a plastic cassette that the user simply dropped into special cameras. The camera would then automatically thread the film. After exposure, the user then took the plastic cassette to the processor who would open it, remove the film, process it and make prints, etc. Both the APS and Instamatic formats also shared the common characteristic that the film was an orphan size - the first Instamatic film was slightly narrower than traditional 35mm and was perforated on only one edge, while the second generation instamatic was a tiny 16mm width that worked just fine for 4x6 drugstore prints, but was unacceptably grainy if enlarged to any degree. APS was also a narrow film, but it also had a data track along one edge.
Both the Instamatic and APS formats were attempts to expand the photography market by producing dumbed-down products for people who were incapable of dealing with the mechanical challenge of loading a 35mm camera. The cameras were all simple point-and-shoot, fixed focus box cameras. APS never really found a strong market, and the introduction of point-and-shoot 35mm cameras that automatically loaded and threaded film pretty much killed the format.
DX film is ordinary 35mm film in a special cassette. The only thing special about the cassette is the way it is painted - there is a pattern of rectangles on the side of the cassette that is the encoded film speed. DX cameras have a set of contacts in the film compartment that read the film speed from coding on the cassette. It's generally not possible to manually enter a film speed in a camera that requires DX coding, but DX film can be used in conventional 35mm cameras.
As far as I know, all commercially-packaged film today comes in a DX packaging, so you should not have a problem getting materials for your class. The APS format, by contrast, is essentially obsolete and may be hard to find.