The FamilySearch Catalog can be thought of as the Browsable Collections finder. It searches all the collections that are available throughout the FamilySearch universe. Collections that have been microfilmed can be discovered. Collections that have been digitized but are only available at a Family History Center facility are listed. Collections that have been digitized and that can be browsed from anywhere can be listed and then displayed one image at a time. In total, the catalog includes books, online materials, microfilm, microfiche, and publications.
I personally think of the Catalog as the means for me to view collections via my own microfilm machine, only via a computer. In my opinion, the Catalog is the most useful undiscovered part of the FamilySearch sets of collections.
To access the site, go to: www.FamilySearch.org/search/catalog
Once there, a user can enter a combination of Places, Surnames, Titles, Authors, Subjects, and Keywords and then browse through the results to choose which ones to view or research further.
There are some tricks to getting the most out of a Catalog search. I strongly encourage you to read this article:
Click HERE for other Free Online Genealogy Websites of the Day