Component in/out is a set of three wires that are used to transmit video information. Component out/in supporting devices come with red, yelow and green cables: two carry color information and the third carries luminance/brightness information. Component signals provide much better video quality to the more commonly used single line video transmission, namely composite signal. This is the kind that comes with only one yellow cable.
S-Video is another format of cable that wraps two cables into one cable and is also considered component. It comes in a single balck wire.
Composite has the lowest video quality, whereas s-video and component devices have the best video quality.
If u want to remember, Component carries the components of a pictures (RGB), composite carries a composited signaland s-video is Special.