The VGA cable, which runs between most computers and monitors, is actually a bundle of 15 much smaller wires, wrapped in thick rubber insulation. These all play a critical role in relaying video and other data back and forth.
Red, Green and Blue
The three largest wires inside the cable carry red, green and blue video signals to the monitor, which then combines them into a full-colour display.
One of the very thin wires carries a simple signal to the monitor, telling the monitor to start drawing a new frame. Entire frames are drawn at a minimum of 60 times per second.
Another thin wire carries a signal to the monitor, instructing it to draw another horizontal line within the frame.
Four of the wires transmit identification information about the monitor back to the computer, and the computer uses that information to trigger driver installs or communicate preferred settings, such as resolution or colorimetry.
Five of the wires are classified as "ground," which complete the signal's circuit for red, green and blue individually, plus one for both sync wires and another general ground.