Comic timing is the use of rhythm, tempo, and pausing to enhance comedy and humour. The pacing of the delivery of a joke can have a strong impact on its comedic effect, even altering its meaning; the same can also be true of more physical comedy such as slapstick.
A beat is a pause taken for the purposes of comic timing, often to allow the audience time to recognize the joke and react, or to heighten the suspense before delivery of the expected punch line. Pauses, sometimes called "dramatic pauses" in this context, can be used to discern subtext or even unconscious content—that is, what the speaker is really thinking about. A pause can also be used to heighten a switch in direction. As a speaker talks, the audience naturally "fills in the blanks", finishing the expected end of the thought. The pause allows this to happen before the comedian delivers a different outcome, surprising the listener and (hopefully) evoking laughter.
Jack Benny and Victor Borge are two comedians known for using the extended beat, allowing the pause itself to become a source of humour beyond the original joke. George Carlin and Rowan Atkinson are two other stand-up comedians considered to have superior timing.
Carlin's most famous routine was his "Seven Words You Can't Say On Television", in which much of the humour is derived from a sudden, rapid-fire delivery of the seven words. The remainder of the routine was a mock-scholarly analysis of why these words are not as bad as the world would have us believe. Here, comic timing is used again as Carlin moved from the rapid list to a more reasoned dissection of the words.
Atkinson is another example of timing in this regard. His "No One Called Jones" routine involves his reading a class roll of students at what we can assume is an exclusive English boarding school. In one version of this routine, each name is a double entendre. In this sort of routine, it is very important to use beats, as simply racing through the list would spoil the effect of many of the jokes.