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).
Refresh rates below 75 Hz can produce an often-imperceptible flicker that can cause eyestrain after long viewing. While some cards can support as high as 120 Hz, sometimes even higher, it is recommended you run 85-90 Hz; rates beyond 90 Hz add an unnecessary processing burden to the eyes. Finally, an LCD does not have a refresh rate; however, if you need to set a rate, values of 40Hz or 60Hz can be used.