A standard for audio/video cables and connectors. HDMI carries video and audio over a single cable. It supports high-definition (HD) video and multi-channel audio (surround sound.) It carries an all-digital signal, ensuring high quality. It also supports DRM, to prevent copyrighted content form being copied illegally.
Standard HDMI cables are commonly used to connect video sources (such as cable, streaming, and other "set top" boxes) to a television.
Some high-end phones can output video as an HDMI signal via the phone's USB-C connector, using a special feature of USB-C called Alt. Mode. This requires a special USB-C-to-HDMI adaptor cable.
See: Alternate Mode
At one time, before USB-C became standard, a very few phones had a dedicated Mini-HDMI (Type C) or Micro-HDMI (Type D) connector right on the phone.