Thanks for responding raincoaster.
As far as I can tell, selecting either a tag or a category from the sidebar widgets produces a collection of my posts that contain that tag or category. If I select one from the body of one of my posts, I'm taken to the WordPress.com Blogs about: page. I'm not sure how the linkage here works, since only tags are shown for the blogs listed and don't always include the tag I clicked on in my post - but the blogs are related.
I started my blog on Blogger back in November, then imported to WP in February. As of now I have a total of 90 categories and 60 Tags that I have accumulated, of which I generally use a total of 15 to 20 per post. These grew out of the belief that they were like keywords that can be searched for. So I figured that the more ways I can identify what a post is about, then the more likely someone will find it. However, I recently read that exceeding 12 total keeps me from being considered for the WP hot blog list (at least I think that's what it meant).
The problem is that nowhere have I found a good statement of how they SHOULD be used to best effect for attracting readers to my blog.