What is nano second?

A nanosecond is a unit of time equal to one billionth of a second (1 ns = 10^-9 seconds). It is used to measure very short time intervals, such as the time it takes for an electronic signal to travel a certain distance, or the duration of light pulses in fiber optic communication systems. In electronics and computer systems, nanoseconds are used to measure the speed of operations and the delay of signals, among other things.