You'd think you could enter any topic as a Subject search in tomCat. However, the Subject search uses special terms to organize books by subject. These are called Library of Congress Subject Headings (LCSH for short). If you enter your keywords as a Subject Search, you may not get much back. For example:

If you entered a Subject Heading search for: acquired immune deficiency you would get no books!

But if you searched using the LCSH term, AIDS (Disease) you'd see the library has several books.