Video Cards

Your system's video card is the component responsible for producing the visual output from your computer. Virtually all programs produce visual output; the video card is the piece of hardware that takes that output and tells the monitor which of the dots on the screen to light up (and in what color) to allow you to see it.

Like most parts of the PC, the video card had very humble beginnings--it was only responsible for taking what the processor produced as output and displaying it on the screen. Early on, this was simply text, and not even color at that. Video cards today are much more like coprocessors; they have their own intelligence and do a lot of processing that would otherwise have to be done by the system processor. This is a necessity due to the enormous increase both in how much data we send to our monitors today, and the sophisticated calculations that must be done to determine what we see on the screen. This is particularly so with the rise of graphical operating systems, and 3D computing.

The video card in your system plays a significant role in the following important aspects of your computer system:

Performance: The video card is one of the components that has an impact on system performance. For some people (and some applications) the impact is not that significant; for others, the video card's quality and efficiency can impact on performance more than any other component in the PC! For example, many games that depend on a high frame rate (how many times per second the screen is updated with new information) for smooth animation, are impacted far more by the choice of video card than even by the choice of system CPU.
Software Support: Certain programs require support from the video card. The software that normally depends on the video card the most includes games and graphics programs. Some programs (for example 3D-enhanced games) will not run at all on a video card that doesn't support them.

Reliability and Stability: While not a major contributor to system reliability, choosing the wrong video card can cause problematic system behavior. In particular, some cards or types of cards are notorious for having unstable drivers, which can cause a host of difficulties.
Comfort and Ergonomics: The video card, along with the monitor, determine the quality of the image you see when you use your PC. This has an important impact on how comfortable the PC is to use. Poor quality video cards don't allow for sufficiently high refresh rates, causing eyestrain and fatigue.