There are 2 main types of 

DVI Cables and Adapters

There are 2 main types of DVI Cables, DVI-D that support digital only and DVI-I that support digital and analogue. Both cable types are also available as single link or dual link, most users will only require a single link cable unless very high resolutions and equipment that supports dual link. DVI-D cables have pin configuratins of 18+1 for single link and 24+1 for dual link, DVI-I cables have pin configurations of 18+5 for single link and 24+5 for dual link. DVI-I cables have 4 extra pins around the horizonal pin, these are used for the analogue signal DVI-A. A DVI-I plug will not it into a DVI-D socket due to the extra pins, however a DVI-D plug can be connected to a DVI-I socket. DVI Cables can be longer using a DVI Extension Cable.