Pictured above is XtremeMAC's XtremeHD HDMI-to-DVI adapter cable. This cable is used when you are are connecting a component (such as DVD player) that has an HDMI output to a Television that may only have a DVI input connection.
In this photo, the HDMI connection end is the small one at the top, and the DVI connection end is the larger one at the bottom.
DVI stands for Digital Visual Interface. A DVI interface connection can transfer a digital video signal from a source component (such as from a DVI or HDMI-equipped DVD player, cable, or satellite box) directly to a video display that has a DVI input connection. DVI can transfer both standard and high definition video signals.
For a review of XtremeMAC's cable products, refer to my article: XtremeMAC HDMI and Audio/Video Connection Solutions - Review.