Salesforce Fact #683 | Simple & composite filters
From the perspective of query optimizer, A query filter can be simple or composite. A simple filter is one where each of the field expression in the condition filters uses the 'AND' operator. Whereas, a composite filter is one where two or more field expressions in the condition filters uses the 'OR' operator. Reference: https://help.salesforce.com/s/articleView?id=000385218&type=1