The refresh rate of a monitor (in Hz) is the number of times the picture changes in one second. Worded differently, the number of frames per second. E.g., if it's at 60Hz, it goes through one frame every 0.0166(...), or 1/60th seconds. At 75Hz, it's 0.0133(...), or 1/75th seconds. There's not too much of a difference, so if I were you, I'd leave it at 60Hz if it's looking buggy. Human eyes typically can't distinguish between 75 and anything above 75. But it's always nice to have a higher one, especially for gaming. That extra 0.0033 can make all the difference, lol.
@CompMan:
Look up what monitor you have, and it should give a refresh rate under its specifications. Most LCDs are 75; however, I have seen some that only go up to 60.