The Library of Conress established a set of subject headings, which IUP's cataloguers use to classify and shelve the books we have in our collection. Subject Headings form what is called a "controlled vocabulary," which simply means that the terms used to describe a book's subject(s) are selected from the list of "acceptable" terms. This way, all books that cover a particular topic are labeled with the same subject heading, no matter what terms the authors decide to use.
The result? Books on the same topic are grouped together, and it makes it much easier to search for books on a topic!
To use subject headings in your searches, you can do a Subject Heading search in the Library's online catalog by entering a keyword into the search page, selecting "Subject Heading Search," and clicking Search. This will give you a list of subject headings containing that term. However, it's sometimes easier to do some general searching until you find a book that addresses the topic you want to study, and then look in the catalog at the subject headings that are assigned to that book. Clicking on the subject headings you see there will take you to lists of other books that share the same subject.
Finally, if you have some time, and want to browse the available subject headings, take a look at the Library of Congress Subject Headings books - the four large red books at the IUP Libraries reference desk in Stapleton Library.
The Importance of Being Earnest's London
The Cherry Orchard's Russia