Traditionally, the Library catalog has been a searchable listing of items owned by the Library: print and electronic books, journals, government documents, videos/DVDs/CDs, etc. Increasingly though, libary catalogs also contain records for selective websites and documents freely available on the Internet.
You generally use the Library catalog:
NOTE: You typically cannot use the Library Catalog to find individual articles within a journal--you may need to use a separate journal index/database for that (See Finding Articles)--although many libraries are now purchasing "discovery" tools that allow the searching of the catalog and article databases together in one search.
To search the Library catalog by topic, begin with a keyword search: type in one or more search terms representing the main concepts of your search (e.g., "pesticide residues and food"); click on a title of interest and use the subject "hotlinks" in the cataloging record to locate other books on the same topic. You can use the truncation symbol (usually an *) to retrieve alternate forms of a word (e.g., food contamina* will find food contamination, food contaminants; food label* will find food label, food labels, food labelling).