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).
This should display your current Refresh rate in Hz. The refresh rate is the number of times per second your display is updated. For standard monitors this should be set to 70Hz at a minimum, otherwise you are likely to see a flickering effect which can cause eyestrain, migranes etc.