A graphics card's job is to do exactly what it sounds like. It sends the graphics elements from the computer to your computer monitor. These graphics can be your programs, pictures or even video. Inside the computer it is all 1's and 0's. The graphics card translates these into a picture your monitor can display. How powerful the card is will determine it's capabilities. This really comes into play with gaming, CAD or other graphics rendering, particularily 3D elements.

The best cards out there make short work of even the most intense graphic elements. Most users, though, don't need that kind of performance. This is why so many lower end systems include less robust "on-board" graphics chips. These differ from graphics cards (which can be removed and upgraded to a better model) in that they are built into the motherboard. Many of these chips share memory with the main system, so they aren't suitable for advanced 3D gaming use.

A capture card allows you to digitize analog video into your computer. It has analog video connections on it so you can connect a VCR or analog camcorder. Many newer capture cards also include firewire ports so you can connect your digital devices, too. Some cards, such as the ATI All-In-Wonder series of cards, also have 3D processors on them so they are good for moderate gaming, as well. These cards even include TV recording capabilities with DVR software.