DVD disks are the most commonly used video storage media. They are the same shape as audio or data CDs, but the information is stored at a higher density. The combination of the higher storage capacity and MPEG compression allow a DVD disk to hold a feature length movie and some extra features.
DVD originally stood for "Digital Video Disk". DVDs have since become used more commonly for data and audio, and members of the DVD forum (the industry association in charge of the DVD format) have suggested that DVD stand for "Digital Versitile Disk". "Digital Versitile Disk" is now used on the DVD forum's website.
With the sucess of the DVD format, there are now camcorders that record direcly to a special DVD disk.
For more information, see the Wikipedia article on DVD