The higher the refresh rate, the less lag you'll notice while watching a fast-paced game. Refresh rate essentially dictates how fast the screen updates the image to keep up with whatever you're watching. Officially, this is measured in Hertz (Hz), with the number preceding Hz referring to the number of times per second the screen refreshes the image. 60 Hz is the number you'll come across in most budget and mid-range TVs, while premium models usually jump to 120 Hz.