A graphics processing unit or GPU (also occasionally called visual processing unit or VPU) is a specialized processor that offloads 3D graphics rendering from the microprocessor.

What's the Purpose?

3D gaming

3D games have been the driving force behind the video card industry’s phenomenally fast-paced growth. 3D gaming is one of the most GPU intensive activity the PC can go through.

Video playback

The latest video card products add not only new features for a better 3D game experience, but also features that cater to advanced video requirements, which, for example, include hardware acceleration for High-Definition video decoding. Without the help of the video card, the CPU would have a very tough time playing High-Definition video and the result could be heavy frame skipping.

General purpose 2D

General-purpose 2D applications include web surfing, word processing, and picture viewing. Such applications are widely used by home and office users and do not have any special requirements for video cards. Usually onboard video cards are ample for this.

What one should i get?

When looking for a graphics card keep a few things in mind.

Onboard GPU

A good amount of your mid range motherboards have onboard GPU, these are ample for general purpose 2D, but for anything else its a good idea to get a separate Graphics Card.

ATI/nVidia

Instead of focusing on which of these two companies to choose from, just read reviews to see which one in your price range is better, also look to see if your motherboard supports Crossfire or SLI, if so its recommended that you stick with the accompanied seller. However some motherboards do support both Crossfire and SLI.

ATI-Crossfire and SLI-nVidia.

Recommendations

If you are planning on doing other things other then basic 2D applications , you might want to take a look at these DirectX-10 Cards.

Low-End Video Card- Ati Radeon 4870

Mid-Range Video Card- Nvidia GTX 275

High-End Video Card- Nvidia GTX 295

GPU Checklist

1. Make sure to get a DirrectX 10 compatible card for increased life span.

2. If you are low on cash get a lower end video card and SLI or Crossfire it in the future.

3. Video games are extremely GPU intensive, if you plan on doing a lot of gaming its advised to get a Mid-Range or High-End Video Card.

4. There are 2 connection types to look for PCI and PCI-Express most of your DX 10 cards are PCI-Express, so make sure your motherboard has ample PCI-E slots.

5. Most people don't realize most of these newer video cards are HUGE, make sure to look at the video cards specifications and make sure it can fit into your computer case.

6. Read reviews to see what video card is right for you, remember don't waste money on getting an insane Graphics card if the rest of your parts are not equivalent.