USearch is the main search box on the library homepage and will show you relevance-ranked results (similar to a Google search). When you use USearch, you're actually searching within the Catalogue as well as many of our online databases at the same time. USearch is useful when you want to start off with a broad search and then narrow down your results as needed. Those results could include books, journal articles, and much more. You're more likely to get hundreds or even thousands of different results.
The Catalogue is a searchable index listing everything the library has purchased or licensed, including all print material. It might be easier to use the Catalogue if...
You want to start off with a very narrow or specific search, such as finding out everything the library owns by a specific author or under a specific title.
You need to put a hold on a book or request a book that is currently out on loan.
You want to search by Library of Congress Subject Headings.
You want to search by the call number of the item you are looking for.