How to use categories in mediawiki
If you know how to use a wiki, 'categories' are simple.
To categorise a new or existing wiki page, add the the category name (Talkaoke, for example) anywhere in the page:
That will put the page in the Talkaoke category, and it will appear in all category listings.
This is useful to stop the wiki descending into chaos, so please use it!.
If you want to find out more about categorisation, read the mediawiki article about it.