Think sound waves.......The hertz (symbol: Hz) is the SI unit of frequency. Its base unit is s-1 (also called inverse seconds, or 1/s). In English, hertz is used as both singular and plural.
One hertz simply means "one cycle per second"; 100 Hz means "one hundred cycles per second", and so on. The unit may be applied to any periodic event – for example, a clock might be said to tick at 1 Hz, or a human heart might be said to beat at 1.2 Hz. The frequency of aperiodic events, such as radioactive decay, are expressed in becquerels.
Big ups to Wikpedia for that explination.....LoL.