WordPress Tag
From Wiki @ Karl Jones dot com
In WordPress, a Tag is a label which can be applied to blog posts.
Tags in navigation and allows posts and to be grouped with others of similar content.
Unlike WordPress Categories, Tags have no hierarchy so there is no Parent->Child relationship like that of categories. But like Categories, Tag names must be unique.
Posts Tags screen
In the WordPress dashboard, the Posts Tags screen allows the user to create, edit, and delete Tags.