The Input setup dialog is comprised of two sections:
This allows customisation of the keyboard. The Auto Repeat check box controls the behaviour when a key is help pressed. If Auto Repeat is on then the key will be outputted repeatedly until you release the key.
The Repeat Delay is the time to wait before the first key press is repeated.
The Repeat Rate is how quickly more key presses should be generated after the first repeat.
Note: Only the XFree86 X server supports Repeat Delay and Repeat Rate (though I couldn't make it work on my machine - if this works for you please let me know).
Acceleration sets the speed the pointer should move after the mouse has moved faster than the Threshold.