Q. Define the Refresh Rates and frame rate?

A special circuit known as the Video Controller scans video memory one row at a time and reads data value at each address sending the data out in a serial data stream. This data is displayed by a process known as Scanning where electron beam is swept across the screen one-line-at-a-time and left-to-right. This is controlled by a horizontal and a vertical field produced by electromagnets - one moving the beam vertically and another horizontally.

The rate at which horizontal sweeps happen is known as horizontal frequency or horizontal refresh rate and the rate at which vertical sweeps occur are known as vertical frequency or vertical refresh rate or simply refresh rate or frame rate. The term frame rate is used since actually one vertical sweep means display of a single frame. Because each frame comprises numerous hundred rows, horizontal frequency is hundreds of times higher than vertical frequency. Consequently the unit of horizontal frequency is KHz and that of vertical frequency is Hz.  

The most significant thing is preserving the same frequencies between Video system and monitor. The monitor should support these refresh rates henceforth the supported refresh rates are given with manual of the monitor.  More about this topic will be discussed in section on Monitors.