A collection, typically of Web Log entries. Kinda like a Top Ic. Bigger buckets than Key Word-s.
Purpose:
by having a separate RSS feed for each, a reader can limit himself to just a subset of a writer's flow.
- this lets one potentially avoid cat pictures
this can have value in a Corporate Blogging context by letting an employee track just a certain subset of flow from staff groups like HR
- note that both examples require the category grouping used by the writer to match the criteria on which readers would like to discriminate.
- a reader happening upon a single article can find other "similar" or "related" articles by browing the category.
Typically there's a flat list of CateGory values, with any given entry being assigned to 1-or-more buckets. But Dave Winer is (Nov'03) starting to use a hierarchy of categories - a Taxon Omy?
see Model Theism
Wi Ki uses categories, more commonly as a page "type" designator. See WikiWikiWeb:WikiCategories - these are used with Back Links as a searching mechanism.
But in a sense, every Wiki Word As Tag.