All PCs require special circuitry that is used to make the text
and graphics images that you see on your display.
Most new PCs are equipped with motherboards that have integrated video chip sets in them. These integrated chips compete with other devices in the PC for access to the main memory. This causes congestion and slowdown.
A solution to this congestion is the Advanced Graphics Port (AGP) found on modern motherboards. It provides a place for a video card to plug in to the motherboard giving it a fast, clear path to the RAM main memory. Besides the fast path to RAM, the video card also has its own local memory anywhere in size from 32Mb to 128Mb which it uses to hold and manipulate the video data before sending it to the display.
Newer video cards also have a DVI connector which provides digital video signals that directly drive LCD displays equipped with a DVI connector. This type of connection provides very good looking video, but keep in mind that not all LCD displays have DVI connectors to take advantage of it.
Fast moving 3D graphics writes millions of bytes per second to the display and high performance video cards are key to realistic looking video. Running high demand video applications without one can make your display look like one of those jerky frame-by-frame TV feeds from reporters in some remote part of the world using portable, but very slow transmission equipment.
Recommendation:
For general, everyday PC operation, the integrated video chips should work adequately.
If you want to run intense applications or video games that require fast, rich graphics, then you'll need a high performance video card. Radeon video cards from ATI and GeForce cards from nVidia are among the top brands offered.