I just added the first cut at a tagging feature. You can now tag Recipes, Testimonies, and Questions. If you want to read about the theory of it, here is Wikipedia's page on tagging.
But it's a pretty simple notion to grasp. Have you ever used file folders to organize your papers? If so, did you ever put labels on those folders (e.g. "taxes 2007", "electrical bills", etc.)?
Those labels are what we call "tags" on the web. The difference between your paper file folders and web tagging is the following: Any specific paper document could be organized into only one folder at a time (and thus under only one label), but the same web document can be organized under multiple tags.
The web way is, of course, a much more natural way of organizing information since any piece of information can always be classified differently under different schema.
Moreover, on the web, when all members are assigning their own tags to the same set of content, multiple different classification schema emerge. Some will be popular shema; others less so.
But over time, as the content becomes thoroughly tagged, any person seeking any type of content should be able to find it through the tags.
If that's confusing, just play with the feature, and over time, you'll see what I mean.