A useful feature of your blog is the ability to create Categories, allowing you to arrange your articles or photos by topics that you create. This post was made to the "Animals" category - or Topic - of the Photos category.

So in this case, the Animals category is a sub-category of Photos....

You can make a post part of more than one category if you wish. I am going to make this post part of the Photos and the Animals categories, so it will appear in either category.