The refresh rate is the number of times a display’s image is repainted or refreshed per second. As it denotes a frequency of a process, the refresh rate is expressed in hertz. That is, a refresh rate of 75 Hz means the image is refreshed 75 times in one second.
Frame rate, or frame frequency, is the frequency (rate) at which an imaging device produces unique consecutive images called frames. The term applies equally well to computer graphics, video cameras, film cameras, and motion capture systems. Frame rate is most often expressed in frames per second (FPS), and is also expressed in progressive scan monitors as hertz (Hz).