Dual Link: Dual T.D.M.S. (transition minimized differential signaling) "links". DVI can have up to two TMDS links. Each link has three data channels for RGB information with a maximum bandwidth of 165 MHz, which is equal to 165 million pixels per second. Dual-link connections provide bandwidth for resolutions up to 2048 x 1536p.
 
Single Link: Single T.D.M.S. link. Each link has three data channels for RGB information with a maximum bandwidth of 165 MHz, which is equal to 165 million pixels per second.
Bandwidth for a single-link connection supports resolutions of over 1920 x 1080 at 60 Hz (HDTV).
 
Dual link vs Single Link: Don't believe the "hype" some websites are using about dual link cables being superior to single link cables. A single link cable is 100% as good as a dual link cable for single link equipment which covers about 99.5% of current equipment, including HDTV's, Projectors, Plasma Screens, and High Definition Set top Boxes. If your equipment does not specifically state it is Dual link in its specifications, it almost certainly is not. A better quality cable is a better quality cable, and single and dual link has nothing to do with quality. On the other hand, if both devices being connected support Dual links, then a dual link cable is the proper cable for the application, and you will have the capability of much greater resolutions and refresh rates. A properly designed Dual link cable should have no negative effects when used with single link equipment.