The title says it all. Specifically, it will help with creating Cores which require map space but are less (or more) than 5x5 cells.
I don't know the internal workings, but this might be a copy/paste from the backend for the CRPL
GetUnitAttribute
CONST_CELLWIDTH
CONST_CELLHEIGHT
Recently asked about in http://knucklecracker.com/forums/index.php?topic=23401.msg156206#msg156206