it'a all a bit confusing. fuji makes 2 types of film:
- instax film
- pack film
the instax film comes in 2 formats: instax mini and instax wide. this is integral film, there is nothing to peel apart. it does not fit into polaroid sx 70 or 600 cameras. it's for special fuji cameras like the 7s for the mini and the 210 for the wide. and there are 2 lomo backs for it as well.
the pack film comes in 2 formats as well: 100 format and 4x5" format. these are peel apart film and they are well compatible with polariod pack film cameras. the 100 film goes into the famous folding polaroids, most of the cheap plastic cameras as well (but keep away from the 80 series). it's also compatible with most of the polaroid backs for the mf cameras as mamiya and hasselblad. and there is a holga back as well.
the impossible project tries to get film ready as a replacement for the sx-70 and the 600 polaroids. this is integral film that comes with a battery at the bottom of the cassette which the polaroids need to function. it's still far away from the old polaroid, but they are making progress. to add some confusion to the matter: they are also selling stocks of old polaroid pack film.
google helps a lot to find out. and if there are still questions, there is this wonderful forum.