The Set Inspectors treat a list of objects as a mathematical set. These sets, in turn, can be manipulated with traditional set operators like union and intersection.
You can create sets from individual elements, separated by semicolons:
elements of intersection of (set of ("to";"be"); set of ("or";"not";"to";"be"))
which returns the list: be,to.
Or you can create sets from ordinary lists, for example:
intersection of administered computer sets of bes users whose (name of it is "joe" or name of it is "sue")
which returns the set of computers administered by both Sue and Joe.