240Hz refers to the refresh rate, and the refresh rate refers to the number of times the image on the screen is repeatedly scanned by the electron beam. The higher the refresh rate, the better the stability of the displayed image (picture).

The refresh rate will directly determine its price, but because the refresh rate and resolution are mutually restricted, only the display with high refresh rate at high resolution can be called excellent performance. If you buy a monitor with a refresh rate of 240Hz and a resolution of 4K,