Re: How are SCN "categories" to be used?

Tammy is correct: categories appear on the content tab, top left.  When you click it, it will filter the content list for content where the category was selected. There's even a URL for the category: http://scn.sap.com/community/gui/content?filterID=content~category[sap-screen-personas]

This allows the classification of content within a space until a sub-space is warranted.  It's employed across SCN, such as on SAP for Mobile.

If the category doesn't apply, it need not be selected.