The refresh rate is how many images a monitor can diplay in one second. It is given in Hz, and generally, the higher the refresh rate, the smoother the picture. A higher refresh rate puts less strain on the eye. You will most likely encounter a 60-75Hz refresh rate, with gaming monitors reaching up to 200Hz.
The refresh rate indicates how many times the image on a screen is redrawn per second. Higher frequencies mean not only sharper edges during moving scenes but also less eye fatigue. Therefore, a refresh rate (or framerate) of over 120Hz are sometimes referred to as "flicker free", as the image does not blink. It's great for long office hours and game play.