Ohoh, don't mischange component and composite...
Here is the solution (I work as a technical director at a TV station

:
1. RGB
The best and original color system.
You have three lines: Red, Green and Blue.
(some RGB, such as RGB cables on computers, also need horizontal and vertical sync lines, but the picture itself uses three lines).
2. Component
Developed by Sony.
Component also uses three lines, but the three lines consist of:
Y
R-Y (or Cr)
B-Y (or Cb)
Y usually is the green line from RGB, R-Y and B-Y are pure mathematical calculations. Y is the luminance (so, if you only connect Y, you get a nice B/W signal).
A component signal can also be YUV, U is a reduced Cb-signal and V is a reduced Cr signal.
Component has been developed when RGB only had 5 lines to get the same image quality with only 3 lines.
3. Y/C (some VHS-recorders also call it SVHS)
All the colors are put together on one line and the luminance gets one line.
So we have a total of 2 lines, but we get some loss in the colors (you won't see them, though, they're minimal).
4. Composite (also called CVBS)
That's the worst quality. The colors and the luminance are together on one line.
The bandwith per line is 5 MHz, the color is encoded (AM) at 4,43 MHz.
For those who want to know a little more:
The more the contrast changes, the higher is the frequency.
(e.g. if you have a striped shirt, you have a high frequency).
When you have a contrast change at exact 4,43 MHz, the TV doesn't know whether this is luminance or a color. That's why you have nice flirring colors at shirts with striped shirts

)
And because we only have small bandwith for the colors, they are really blurry at edges.
Oh, and none of the four signals here are digital, all pure analog
Okay... I hope this is all you ever wanted to know (if you want to know more, just ask

)