Here is a visual representation of the AND, OR, and NOT operators.
Diagram by Duke University Libraries. CC BY NC-SA
This example also demonstrates how quotation marks can be used to retrieve only exact phrases. The example of the AND search will retrieve only works that include Toni Morrison, with her name written exactly that way, and Nobel Prize. If an item simply says that Toni Morrison won a Nobel without the word prize, it will not be returned in this search.