Pause[n] pauses for at least n seconds.
Pause is accurate only down to a granularity of at least $TimeUnit seconds.
The time elapsed during the execution of Pause is counted in SessionTime, but not in TimeUsed or Timing.
Under multitasking operating systems, there may be a delay of significantly more than n seconds when you execute Pause[n].
See The Mathematica Book: Section 2.13.3.