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.