HDMI, or High-Definition Multimedia Interface, is a common interface for transmitting uncompressed digital video and audio streams. The HDMI system provides an extremely high data quality of both video and audio in a single cable, and is therefore rapidly becoming the standard for many different devices, including Blu-ray players, gaming consoles, and LCD and Plasma Televisions; HDMI ports also exist on some newer computer multimedia cards.
Like many other computer cables, manufacturers produce HDMI cables to an increasingly strigent level of specifications. Newer cables have even more bandwidth than their predecessors, but are backwards compatible, meaning they can work with older HDMI-capable devices. The newest widely-available HDMI cables meet the 1.3b standard, and it's best to purchase HDMI 1.3b cables if possible.
HDMI cables feature connectors with 19 pins on both ends of the cable. These pins allow for both High Definition video and audio to be transmitted at very high speeds.