Hertz

Hertz (or Hz for short) is unit of frequency, in cycles per second. One Hz is one cycle per second.

Common uses of Hertz include specifying sound pitch, processor clock speed (usually megahertz), and electromagnetic spectrum; such as the frequency of visible light (790–400 terahertz).

The frequency of the mains in a building, or power generated by a generator are also shown using hertz as the unit.

North America uses 60hz AC, whilst other parts of the globe use 50hz AC