First you set up your own categories on your site - whatever you want, and whatever your site is about. If it is about animals in general, you might have categories such as dogs, cats, horses. Each of these (depending on what CMS/blog software you are using) may then have sub-categories, eg in dogs, you might have poodles, terriers, dachshunds.

Then in the plugin you can select which of these categories are to receive articles.

Once you have done that, the Wizard will then match the categories assigned to the article by the author, to the list you have provided. If a match is found, you will receive the article. If no match, then you won't.

If you have a broad category such as "Business", you will receive loads of articles (unless you specify a daily maximum). But if you have a tightly niched category such as "Jack Russel Terrier" you will receive very few.

The received articles will be placed in just one category. If your system supports tags (eg Wordpress), then the article will also be tagged with the first few keywords provided by the author.

By playing a bit with your categories you should be able to find the right mix for your site.