Boolean operators (AND, OR, NOT, and sometimes NEAR) allow you to specify logical relationships between search terms—to limit, broaden, or define your search—thus leading to more useful results. You will see these options in library catalogs, databases, and search engines. It helps to experiment with different search terms and try different combinations for more relevant or different results.
A search for teaching AND learning narrows results to only items that include both terms.
A search for teaching OR learning broadens results to items that include either term.
A search for teaching NOT learning limits results to items that include teaching, but eliminates any results that also include learning.