They are two different things and not related. The refresh rate is the number of times an images is displayed per second, so in theory, a 120Hz set displays an image twice as many time. Response time is how fast a colored pixel on the screen turns white and then to a color. A 6 millisecond response is better than 8. My Sony has a 2.5 millisecond response time. Plasmas don't really have to deal with this because they are phoshphor-based technology like tube TVs. Your second question can't be answered because the two are unrelated.
Is the pixel response time the same as the refresh rate? If not, how many miliseconds response time is equivalent to 120hz refresh rate?