FPS stands for Frames Per Second. Its more or less how many images appear on the screen in a given second. The lower the FPS the more stuttery it becomes because of well... The lesser amount of Frames in a second.
Thats not to say a fps as high as you can possibly imagine is a good thing, nope, quite the opposite with current technology. Most current monitors are limited at 60fps, some gaming oriented monitors are limited to as high as 144fps, going over this amount is detrimental due to the simple fact we get screen tearing where say you see an image but the monitor isn't refreshing fast enough to process all the images that are coming into it so it either jumps ahead or something to that affect.
I'm pretty bad at explaining things so if you didn't understand, please ask.