well d33pt, its an easy concept, but it's hard to explain. hehe
regular widescreen discs the black bars are actually part of the picture and encoded on the movie.
Anamorphic movies use the whole area for picture and stretch it out to make stuff tall and thin.
Then when you have a widescreen tv, or a tv that can do the squeeze, it squeezes the info down, so it looks right.
to simplify it, anamorphic discs have about 33% more resolution than non anamorphic ones.
fvck it, go here and this will explain all.
ANAMORPHIC DEMO