What is "micro-scale" building? I have seen references to "micro-scale" building in LEGO documentation. How is this different than the "normal" LEGO building scale?
It refers to building items at a much smaller scale than the usual "mini-fig" scale.

For example the "Micro" Star Destroyer:


 4492 Mini Star Destroyer



Edit to add:

Officially however, when bought as a set they are usually referred to as "Mini-scale".