HDMI (High-Definition Multimedia Interface) is a digital connection standard that allows transmission of video and audio data between devices such as Blu-ray players, video game consoles, and HDTVs. It transmits encoded video and audio data digitally using TMDS (Transition Minimized Differential Signaling). There are different versions of HDMI from 1.0 to 1.3 that offer increased bandwidth. While HDMI is backward compatible with DVI, HDMI provides additional features like audio and device control capabilities. HDMI specifications include electrical and mechanical requirements for cables and connectors to support various video formats and resolutions.