Screen resolution (1024x768, 1280x1024, 1600x1200, etc) -- look at the details to see exactly what the resolution is.
Is higher resolution better? That depends on how good your eyesight is
With LCDs they have only one resolution, unlike CRTs that have a
maximum res. LCDs must fake any lower resolution by either turning off part of the screen like a widescreen DVD, or by filling in approximate pixels in between the real ones (which can look pretty bad).
One drawback to ultra-high-resolution is gaming: a laptop graphics card won't be able to run many games at the real screen resolution if it is 1600x1200 and will have to fake it with the in-between pixels and the flaven.