Subject Headings are used as a way to index and organize information based on the topic of the work. They are a form of controlled vocabulary, which means that certain words/phrases have been selected for use and are used consistently.
English is a big language. There are often many ways to express an idea. For instance, an author has written a book about teen culture in the United States in the 50s. What should the book's title be?
For teens, you could also use teenagers, adolescents, youth, or even young adults
The United States could also be America, the US, or the USA.
The 1950s could be referred to as the mid-century period, cold war era, atomic age, etc.
You could do a dozen different searches and still not find all the relevant books. Subject headings help link together books on similar topics, making it easier to find them.
Subject headings need to be looked up-- it is impossible even for most librarians to guess what the official subject headings will be for a topic!
The following video shows how to find and use subject headings in the WCU library catalog. For Worldcat, see the next page down on the guide.