[link|http://www.dvdtimes.co.uk/content.php?contentid=244|Widescreen Unravelled Part 4 - Anamorphic DVDs]
Many DVDs are described as being "anamorphic" or "enhanced for widescreen/16:9 TVs" (both mean the same thing) - and if you've read any of the reviews in DVD Times, you'll probably have picked up the impression that these are very desirable things (and you'd be right).
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But if you play an anamorphic DVD on a 16:9 TV, the difference is dramatic, because the TV can "unsqueeze" the image so that it fills the entire width of the frame, recreating the original image at the highest possible definition given the current limitations of domestic TVs (and the aspect ratio of the original picture: 2.35:1 films will still show black borders). The result is a picture that offers up to 33% greater definition than a non-anamorphic DVD.