XtremeComputing posted a review on the Arctic Cooling MX2 Thermal Compound

For those of you who don’t know what a thermal compound does allow me to explain. Its job is to transfer heat as efficiently as possible between a heatsink and a processor (or any other such similar setup). Without a thermal compound in place CPUs would overheat, as there are far too many micro imperfections in the base of a heatsink (and top of a CPU) to be able to effectively transfer heat (not to mention that air trapped between the two would hinder this already poor performance).

Arctic Cooling MX2 Thermal Compound Review