A graphics card is a set of computer chips on a circuit board roughly the size of an index card. The chips are dedicated to a single task: to take video data from the PC's processor and convert it to signals for your monitor. Though most computers have graphics chips built into the motherboard, their capabilities are usually basic. Graphic designers, gamers and multimedia enthusiasts typically purchase more sophisticated graphics cards; these plug into the motherboard and deliver faster graphics processing and better image quality.

Graphics cards connect to a standard motherboard slot, such as the Peripheral Component Interface, PCI Express or Accelerated Graphics Port. The type of slot determines the speed at which the card communicates with the computer's processor; the faster this happens, the more data they can exchange, resulting in an better image. In 2012, the PCI Express standard is the fastest, able to transfer up to 7.8GB per second. As with all computer technology, these standards evolve and improve with time.

The graphics card has one or more connectors that accept the monitor cable. Monitors have a few different standard cable types, including VGA, HDMI and DVI. VGA is the oldest standard, going back to the 1980s and supporting basic graphics with a resolution of 640 by 480 pixels and up to 256 colors. High-definition televisions and monitors use the HDMI connector. Currently, computer monitors have the DVI connector, which supports digital video with resolutions up to 1,920 by 1,080 pixels.

Producing accurate graphical images is a mathematically intensive task; each frame in a three-dimensional image simulation takes millions of calculations. A computer's microprocessor is usually busy with other work, so the graphics card handles this. The card has a chip called a Graphics Processor Unit, a microprocessor specialized for video calculations. The GPU lets the computer's main processor do its job, allowing the computer to run at full speed.

The graphics card's GPU has its own memory, called Video RAM. It serves as a temporary holding area for video data as the GPU generates each image. Because the graphics card doesn't need to share memory with the main processor, VRAM improves the computer's overall performance. Because it processes hundreds of millions of bytes of video data every second, VRAM is fast and tends to be more expensive than standard memory.

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