By default, searches on more than one keyword will find results that contain all keywords (AND) rather than results that contain any of them (OR). However, you can use AND or OR statements to separate individual keywords for greater control of the search results.
For example, adventure AND science would generate results that contain both words (simply typing in adventure science would also generate the same results). However, for art OR liturgy, the results returned would contain both or either words.
Exact matches can be searched for by enclosing keywords in double-quotes.
For example, "short stories" would generate a result set which match the exact phrase.
Brackets can be used for further control on the result set.
For example, adventure AND (science OR liturgy OR "short stories").