HZ HERTZ

Hz stand for "Hertz" which in turn stands for cycles per second.  Hertz (Hz) is a measure of frequency.   For example, if an ac signal were to oscillate - that is to vary its amplitude up and down 60 times a second, we would call that 60 cycles per second or 60 Hz.   1000 Hz is also called 1 KHz (kilohertz).  1 million cycles per second is also called 1 MHz (megahertz).  And 1 billion cycles per second is also called 1 GHz (gigahertz).

The term Hertz was named after Heinrich Hertz (who lived in the late 1900s) who proved that electricity could be transmitted in the form of waves.