The processor - otherwise known as the Central Processing Unit or CPU - is the brains in your computer. Without its CPU, a computer could not function at all. This is the magic bit that processes all the instructions and fetches all the data. The two main brands of processor are Intel and AMD. While each one is different, neither is really 'better than the other as far as performance goes.
You can get a single processor with only one chip to do all the calculations or you can get a dual processor with two chips. The dual processor is not necessarily faster than the single, since there are lots of programs that dont take advantage of the dual processor. In fact, some programs run faster on the single.
A Centrino processor is basically a processing chip for laptops put out by Intel. You wont find one anywhere else but in a laptop. MMX, or MultiMedia Extension technology refers to a set of instructions on an Intel chip (processor). While they help programs to run faster, not many programs take advantage of them yet. However, getting one now is a good idea because it will save upgrading in the future.
