Anamorphic wide-screen is literately like putting a rectangular peg into a square whole. It dose not fit but you can force it and doing so will result in an image of the wrong proportions.(so that a normal man is thin and tall). If there where a way to correct the proportions, the image would display nicely.
Lucklerly there is, you know that 'streach' or 'full' setting on your TV that make 4:3 people look short and fat, well if you use that setting on an anamorphic image(which recall is thin and tall), the image will fit the TV like a glove. Why such an exact fit? Well the people that made 16:9 TVs where smart and did that math to make this change work.
If you have a 4:3 TV, your DVD player should be smart enough to persevere the 16:9 original aspect ratio by padding it with black bars on the top and bottom.(it won't fit otherwise).
DVDs aren't the only thing that use anamorphic wide-screen. TV specifications like NTSC only allow for 4:3 images at lower resolutions(like 480i and 480P), meaning streaching the image is the only way to get 16:9. Game systems that run at these lower resolutions like the PS2, Xbox
HD signals have a true aspect ratio(normally 16:9) and no longer use anamorphic wide-screen.
Thanks, I hope you learned something.