When you have an exact title of a book or a journal, an author's name which should be entered last name, first name, or a call number, the first search screen works well and intuitively.  The subject search on the first page is for the exact and formal Library of Congress term.  Plain language often doesn't work here.

But to find a book or overall journal which is about a particular topic, you can enter words in everyday terms on the GUIDED search screen.  Be sure to mark "as a phrase" where that is what you mean.  When you locate books and journals on a topic using everyday language, you can then click LONG view, and see what the formal Library of Congress terms are for your topic.  Double clicking on those terms will bring up other books Princeton holds on this subject.  Also, these formal Library of Congress Subject terms can be used in the WorldCat shared catalog of hundreds of libraries.  Materials you identify in this way can be requested through Princeton's Borrow Direct or Interlibrary Loan services.