Mini DisplayPort is a compact version of the DisplayPort connector introduced by Apple in 2008. Mini DisplayPort is free to license, and in 2009 it was included in the official DisplayPort 1.2 spec. In 2011 Apple and Intel announced the Thunderbolt format, which used the same physical connector, but significantly different protocols.
Screen refresh rate is the number of times an image on any type of monitor or television is reconstructed per second. This is measured in hertz.. (Hz).
LCD screens don't have a refresh rate like the old CRT did. The only thing flickering might be the back light at 200Hz or more. 120Hz refers to the input frame rate from the graphics card. The difference between 60 and 120 at desktop might be near impossible to see, the mouse might move a bit smoother.