The unit of frequency measurement equal to one cycle per second. For example, 30 Hertz means 30 times per second.
This measurement is commonly used for the frequencies of radio waves, sound waves, and much more.
In phones specs, it is common to see Hz as a measure of how often a display refreshes the images it displays. 30 or 60 Hz is common, but 90 Hz and higher can look smoother, particularly when displaying content with very fast motion, such as fast-paced games.
For gaming, Hz can also refer to how many times a second a device checks for changes to a touch surface such as the display. This can improve response time.
Hertz is usually abbreviated Hz, and is named after Heinrich R. Hertz.