Digital Video (DV) Files
DV is a standard format created for consumer digital camcorders, and the DV files on our website appear as a special form of QuickTime file. We offer these files for our older material for which the original frames are not available. DV files can be edited on a frame accurate basis, but are much larger and more inefficient than MPEG files (which can be hard to edit accurately). If you want to simply play a movie, download one of the MPEG formats. If you want a high-quality, editable version of a movie, download the DV format version if it is available and the original frames are not offered.
More information on digital video formats from Google.