Books in Primo are assigned Library of Congress Subject Headings. In many ways, subject headings are a form of tagging, in that they represent the content of the material and provide ways for you to efficiently locate more materials that are conceptually related.
Here are several examples:
There are several databases from which to choose when you are seeking scholarly work.
Don't forget, recommended subject databases for each discipline can also be found on the "articles" tab in each library subject guide.