ArtOfProtoss said:
Micromanagement is the control of one unit or a group of units. Macromanagement is the production of units. To flesh this idea out micro would be controlling a group of goons and preserving the ones at low health. Or it could also be dropping a reaver and aiming his scarabs. Macro would be the production of more goons or reavers.
this can actually be expanded a bit more. Micromanagement also includes anything that falls under "spells" or having to click on one or a group of the same unit in order to use, for example, psionic storm.
Macromanagement is where you control armies (like the prefix implies) and do actions like managing an army on one side of an enemy's base while doing the same on the other side or maybe dividing your units into separate hot-key groups and managing the whole as one attacking force.
The individual management of each group or even unit in the group counts as micromanagement.