I think (and anyone feel free to correct me) that when they are referring to snacks, they mean the 'junk food' that you can purchase just outside of the theatre.
I haven't purchased any of these snacks, as we had the early show and I didn't want to fill up before dinner (although, even if we had the early dinner, I would have been too full anyways), but I remember that they charged for them (not sure how much).
Hope that helps
Katdb