What are Tags and why should I care?
Tags are used to categorize the content of your site. Blog search engines, such as Technorati, use tags to categorize the content of your post.
Most blogging software such as WordPress use categories that you can classify your posts. When you post new content to your site, WordPress pings Technorati with containing those category elements in the RSS. These categories are indexed by Technorati and show up in their search engine.
Sometimes it is not convenient or you may not wish to add new categories to your blog. By simply adding tags to your anchor links on the post, the post will get categorized under the anchor text. You must qualify the anchor link with rel=?tag? for proper categorization.