Many pieces have been written by many people attempting to explain, in terms accessible to the non-technical, what anamorphic widescreen is all about. I’ve had a bash at it myself here and here and, to some extent, here.
But this slide show Web site offers an exceptionally accessible explanation, well illustrated, that ought to be clear to anyone.
Thanks to my brother Mark, whose own Web site is full of excellent photographs of Canberra.