RCA FAQ
What is RCA? RCA is a connector used for audio and video devices. The same connector is used for both audio, video, and digital audio. Most frequently it is used to carry left and right audio to the receiver, or for digital audio. It is also used to carry video to the TV. Sometimes a bundle of RCA cables will carry multiple signals (audio and video) between devices. RCA is sometimes called a 'phono connector'.

RCA comparison chart
Left channel audio
Right channel audio
Digital audio (also known as 'Coaxial' or 'SPDIF'). Typically colored orange.
Video. Sometimes called 'composite video'. Typically colored yellow.
Component video - for HDTV (YPbPr signal method).
Three cables are required to get picture.
Typically colored red-green-blue.

RCA on Wikipedia