In the text entry field you can specify keywords, e.g. foo, bar, baz, boolean operators, i.e and, or, not, and parentheses, i.e. ( and ). Keywords separated by spaces are equivalent to keywords separated by and. The database searches for document names and content containing words that match your pattern (as opposed to documents containing lines which match your pattern). All searches are case-insensitive.
|foo and bar||find documents containing foo and bar|
|foo and not bar||find documents which contain foo but not bar|
|foo or bar and baz||find documents which contain both (1) either foo or bar, and (2) baz|
|foo or (bar and baz)||find documents which contain either (1) foo, or (2) both bar and baz|
Now try it for yourself!