For example, the Xbox One and its variants are limited to a maximum refresh rate of 120Hz when the console is displaying in either 1080p or 1440p. The Xbox Series X, however, supports a 120Hz ...
120 Hz refers to the vertical refresh rate of your display ... Keep in mind that some games, like Anthem, run at 30 FPS on Xbox One X, so they're only boosted to 60 FPS on Xbox Series X.