A Video card or graphics card or graphics adapter is a card in your computer to connect it with your monitor. Video signal is transferred from it via a cable to the monitor.
The most common connector is the analog VGA connector, but the digital DVI connectors are becoming more popular. Some display adapters are also capable of displaying video on TV by an S-Video connector. This capability is called TV-out.
Video cards have a graphic processor and memory dedicated for graphic operations. The most common standard today for display adapters is VGA. Most notable display adapted manufacturers are Nvidia, ATI and Matrox. There is also Linux support for old 3dfx cards.