The Refresh rate governs the number of frames you see in a unit of time, typically one second. It is measured in Hertz, which is a unit of frequency. Thus, it signifies the frequency with which a screen is updated.
The Response Time is defined as the time taken for one pixel to switch on, display the requested color and then switch off. It is measured in milliseconds, as it is a unit of time.
To understand the difference, you need to understand the context.
A low refresh rate will result in a choppy video. So, if you are watching a car in motion, it would appear that the car is jumping across the screen. This is also called motion blur, where you are unable to see an intermediate frame that causes the motion to look distorted. Increase the refresh rate, and the movement seems smooth.
Using the same example, a slow response time will appear as if the car is leaving behind a trail or dimly lit cars; this is also called ghosting. A faster response time of 1ms will appear with just one car moving.