There is a bewildering array of film type numbers that were once produced by Polaroid. Now that Polaroid no longer makes film, any currently-manufactured film that fits a Polaroid is made either by Fuji or by The Impossible Project. So, unless you're thinking of buying expired Polaroid film from somebody, your choices are pretty simple.
1. If you have a Fuji Instax or corresponding modern Polaroid-branded camera, the film is made by Fuji. (Instax film.)
2. If you have a Polaroid pack-film camera (the type where you take the picture, then physically pull the film out of the camera and peel it apart after it develops), the film is made by Fuji (FP100c for color, FP3000b for B&W, or still-available fresh FP100b for B&W, which I think Fuji recently ceased producing)
3. If you have Polaroid camera that uses integral film (the type where the film ejects automatically from the camera once exposed), the film is made by The Impossible Project.
Again, the above types describe what's available in terms of currently produced film. Many old types of Polaroid films are available on E-bay and such. It would probably be a worthwhile blog to try to define the differences because right now, at least to me, these are a bit of a mystery.
By the way, if you have a Polaroid back for a medium format camera, there is Fuji film for that, too.
