When you take the essay sections of the GRE, if you are taking a paper-based exam, you will be hand-writing your essays. If you are taking a computer-based exam, you will be typing your essays.
If you have a choice of one over the other, consider taking the computer-based exam. The good thing about the CAT version of the GRE is that the test actually adapts to your answers — the more you get right, the harder the questions get, and the more points you can achieve.
Some test analysts say that your top GRE score (or the maximum amount of points you can get) is determined within the first ten questions of each section of the test, and that fewer points are credited to you as you go along. This by no means suggests that you should focus on the first ten questions of each section and then slack off. The GRE determines which, if any, universities you're going to get into for your master's degree, so you want to take the whole test seriously and do your best to answer all the questions correctly.