Originally, they limited the angle at which the display could be viewed. Don't let all these acronyms confuse you. Look at the screen from straight on and from different angles. Then compare them against the other screens in the store. If you like what you see, that's all that matters.
Battery power continues to be one of the biggest problems on mobile computers.
More battery means more weight, but few batteries will get you through a full working session on a transcontinental flight. Your choices in portable power are lithium ion, NiMH and NiCad batteries. If you plan to use your notebook regularly on long trips where plugging in won't be possible for extended periods of time, choose a notebook that lets you take out the CD-ROM or floppy drive and insert a second battery. Then there's the issue of pointing devices. Using a mouse isn't always possible if you don't have a flat surface to work on.