Yes, all HD *is* in fact widescreen. A basic description of "HD" is that it has a minimum resolution of 720p (progressive) AND is in 16:9 format.
As for movies that are "wider than HDTV", I don't know how accurate that is either. There are a few "widescreen" formats: 1.66:1, 1.78:1, 1.85:1, 2.35:1. That last one is very common and is often called "enhanced for widescreen TVs". This will actually have the largest black bars across the top and bottom. I guess this one is "wider" than a 16:9 screen.... 1.78:1 is *exactly* 16:9 (16 divided by 9 equals 1.777). A movie in this format will have NO black bars top or bottom. Toy Story I and II are in that format. The other two will have very slight, sometimes not noticable, black bars on the top and bottom.