When you post an article on Universal Hub, you get lists of neighborhoods and topics so you can select which categories the article will appear in. Very handy.
But what if you want to post about something your slug of a site editor has yet to create a category for? Like, oh, Leominster? Or what if the categories aren't specific enough? Like, say, you want to post about something on the Orange Line, and the best you can find is "The T"?
Free tagging to the rescue!