I'm just going to add to my post count here by agreeing.
Really - look at the back of the DVD and it will typically give the aspect ratio of the 'widescreen' DVD. Widescreen is a generic term that refers to EVERYTHING wider than your old 4:3 television. But, a widescreen DVD is designed to make the most out of your 16:9 television's resolution.
It does NOT mean that the actual film is being presented to you in 16:9 format.
As said, most movies are actually 1.85:1 or 2.35:1
Both of which leave you black bars above and below the image.
THIS IS NORMAL!
You are about the 10,000 person to ask that question though, so don't feel like you are the only one who has wondered.