Frame Rate, or Frames Per Second (FPS), refers to the number of frames that make up each second of a video image. The more frames per second the smoother the motion in an image will appear.
When capturing a static image with a stationary camera a slower FPS isn't that noticeable. When the subject or camera are moving a slower FPS will result in a choppier image. As the FPS increases, that choppiness lessens and the image changes will appear much smoother.