The Hertz:

The standard unit of frequency is the hertz, represented by Hz. It was previously known as the cycle per second or merely the cycle. The hertz is a small unit in the real world, and 1 Hz symbolizes a very low frequency. Generally, frequency is measured in millions, billions, or trillions of hertz. Such units are known as kilohertz (kHz), megahertz (MHz), gigahertz (GHz), and terahertz (THz), correspondingly. In terms of SI units, the hertz is mathematically easy, though the concept is esoteric for some people to grasp: It is an inverse second (s^-1) or per second (/s).