What is FPS

FPS (frame per second) means the number of frames played in one second. A typical FPS for hand-drawn animation is FPS 12. 

The speed of an animation depends on the number of frames you have and the FPS. If you have fewer inbetweens (the frames between the keyframes), or a lower FPS, your animation is likely to look clunky.  Even you set up a higher FPS, without enough frames the animation would still look inconsistent.

 Too ambiguous? Try out different FPS settings in Animation and observe the differences.  You can refer to these tutorial posts to find out more,

Set Up FPS (Frame Per Second)