Hertz (Hz) is a unit of frequency that measures how many cycles of a periodic event occur in one second. It is commonly used to describe sound waves, radio waves, and other types of oscillations. For example, a sound wave with a frequency of 440 Hz vibrates 440 times per second, which corresponds to the musical note A above middle C. In addition to sound, hertz is also used in electronics and telecommunications. For instance, the frequency of a computer's processor might be measured in gigahertz (GHz), where one gigahertz equals one billion hertz. This measurement helps indicate how fast a processor can perform tasks.