Sets search categories for this list (by default, none are defined) for the CataList service (see the List Owner's Manual for details). For instance, you might have a list on the topic of great opera tenors of the 20th century, and want anyone searching the CataList based on certain topics to find your list. You might therefore code:
* Categories= Arts:Music:Opera,Arts:Music:Opera:Singers
* Categories= Arts:Music:Opera:Pavarotti
and so forth.