Two important pieces of information about your computer are it's processor speed and the amount of RAM installed. RAM is often referred to as memory. Processor speeds range from 100 to 400 megahertz. The higher the speed, the fewer microseconds you have to wait for something to happen. You will buy a processor based on your need to keep up with the neighbors or the degree to which you suffer from processor speed envy.
Faster ones are great for games.
RAM, or memory, is something you can never have too much of. For modern machines 16 megabytes is a minimum. 32 is better for large file handling and photographs. 64 is more than enough for most people. 128 is for large capacity users or for those who also suffer from memory envy.