Now days you wouldn’t buy any video device without it – HDMI – but what does it stand for:

Short for High-Definition Multimedia Interface, it is the first industry-supported uncompressed, all-digital audio/video interface. It’s a single cable and user-friendly connector that replaces the maze of cabling behind the home entertainment center. HDMI provides an interface between any audio/video source, such as a set-top box, DVD player, or A/V receiver and an audio and/or video monitor, such as a digital television (DTV), over a single cable.
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Via Webopedia