The importance of this particular component is often underestimated by many people, even some of those who know a bit about computers. The misconception is that graphics cards are only benefit gaming systems, which is not the case. The graphics card is responsible for the rendering of 3d visual effects and basically determines how "pretty" your picture looks on screen. While it is true that not all systems have or need a graphics card in order to function, they are standard issue on most modern machines that you will find in stores today.
While graphics card are primarily for the rendering of video and gaming engines, however they present their benefits admidst the appearance of standard PC operations. The maximum output resolution of your computer for example will be determined, in part, by the graphics card you have installed. If you dont have a graphics card at all, then your options for screen resolution will be minimal.
Being able to increase the resolution of your screen gives the advantage of sharper, clearer looking images. If you have ever looked at your screen and noticed that the text, the icons, everything was just BIG, then that is the effect of a low resolution.
The screen of your computer is made up of thousands upon thousands of little squares called pixels. The above image gives you an in-depth look at how pixels work to produce your image. Each pixel displays a combination of red, green and blue, to give it the necessary colour, and you can see how up close, one colour gets blended into another. If you look really closely at your screen, preferrably at something white, you should be able to see these pixels covering the area like a grid. The maximum number of pixels that are individually controllable is determined by the graphics system you have, and how much memory is dedicated to it. This is why graphics cards, which have their own dedicated memory, allow for higher resolutions. More pixels can be individually controlled, allowing for smaller, sharper and clearer images.
When dealing with resolutions, both in windows and in games, they will be referred to in two dimensions. The number of blocks across and down. For example, a fairly standard low resolution is 640 x 480. This means 640 blocks across the screen by 480 down. Just like primary school maths. 640 x 480 = 307200. This means that at a resolution of 640 x 480, the image on your screen is made up of a grid of 307200 coloured blocks.
That may sound like a lot of blocks, however this is one of the lowest resolutions you will find nowadays, and it produces an image that is quite large and not very sharp. Thus we have resolutions that go much higher, with the assistance of a graphics card.
The graphics card is almost like a mini-computer in itself, in that it has its own processor (but specifically for graphics), and its own memory (which is sort of like RAM). Graphics cards range massively is size and capability, and likewise, in price. There are two types of graphics card, as far as compatibility is concerned. The older type is known as AGP (Accelerated Graphics Port). An AGP card can be identified when the connection pins on the underside have a groove around the middle of the connection. The following image shows a typical AGP graphics card.
Along the bottom edge of the card, there is a protruding section with brass coloured contact pins on it. This section is the part that slots into the motherboard of the computer, and therefore to ensure compatibility, the design of this connection is representative of the type of card. While both types have these connections, the AGP cards have a slot closer to the centre (as seen above).
The second type, and the newer of the two, is PCI-E (Peripheral Component Interconnect Express), or PCI Express as it is more commonly referred to. The advantage of PCI Express cards over AGP cards, are similar to those that SATA Hard Drives have over the older IDE Drives. They allow for serial bus data travel, instead of the old parallel type. To put it simply, PCI-E does stuff faster than AGP does.