Graphics controller
Although matters have improved dramatically in recent times, mobile graphics performance is one area where notebooks still lag behind desktop machines, and it's one of the most important aspects of a computer. It's the graphics controller that produces two- or three-dimensional images on the display.
As mentioned above, the graphics processor can be the difference between a 15in display providing a resolution of 1024x768 up to resolutions of 1920x1200.
When you raise the resolution on your display, you add to the graphics board's workload by forcing it to produce a larger number of pixels. Likewise, when you increase the colour depth, it adds to the complexity of the work the graphics controller must perform.
All graphic controllers now easily manage the processing of 2-D images (such as those created when you browse the Internet, work in office applications or even watch a DVD. If this is all the graphics grunt you require from your notebook, then a less-costly, battery saving integrated graphics controller (such as Intel's Graphic Media Accelerator X3100, that shares video with main RAM) should be fine.
Note: these "discreet" (dedicated) controllers are in virtually all instances integrated into your notebook's motherboard, although mainstream notebooks allowing graphics upgrades are around the corner.
However, if you want to play the latest 3-D games at a decent resolution and frame rate or you're a CAD designer, then you'll need a discreet graphics controller from ATI or NVIDIA with dedicated DDR video memory (up to 512MB).
The more powerful a graphics controller you require, the more expensive your notebook will become.
So if a discreet graphics controller is for you, your next step is to decide which brand and type will be most suitable.