Sims 2 Object Categories
From SimsWiki
Object catagories can be used instead of GUIDs to find objects. They are especially usefull when more than one of a particular type of object exists (like counters). They are used in many search routines, like finding a bookcase to put a book back. See List of Object Categories
Object categories are seperate from SemiGlobals, since not every semiglobal group sets a category and not every object with a category has semiglobals.