two trivial questions of two DDK functions

Hi all
    here r two DDK functions .
    RtlMoveMemory and KeDelayExecutionThread ,which is involved in my question.
    i want to know
    1st. what is the difference between RtlMoveMemory and RtlCopyMemory.
    2nd.  what is the difference between Absolute expiration times and  relative expiration times ( the last parameter passed to KeDelayExecutionThread is represented as relative expiration times , if it is a negtive LARGE_INTEGER.)

Any assistance is much appreciated and using chinese is preferable, thanks