Radar
The time between pulses influences how far away an object can be detected. That distance is called the "range" of a radar transmitter and receiver.  Radar transmitters and receivers use slow repetition frequencies to find the distance to objects that are far away.  This makes it possible to accurately determine the distance to the moon, for example.  Fast repetition is used to detect objects that are much closer, like ships at sea, high flying aircraft, or to determine the speed of fast moving automobiles on highways.