The hertz (Hz) is the SI base unit of frequency, defined as one cycle per second, measuring how often a repeating event occurs. From AC power grid frequency (50 or 60 Hz) to audio tones and processor clock speeds, hertz is the universal language of frequency. One hertz equals exactly one cycle per second.

The gigahertz (GHz) equals one billion hertz, the standard unit for modern CPU clock speeds, Wi-Fi frequencies, and 5G cellular bands. A typical laptop processor runs at 2–5 GHz, while Wi-Fi operates at 2.4 GHz or 5 GHz. One gigahertz equals 1,000 megahertz or one billion cycles per second.