"Keyword" allows you to combine terms using "and," "or" as well as "not" operators. A blank space is interpreted as an "and." "not" can only be used at the end of a search string.
eg. "music journal not educator" would find all titles using the words "music" and "journal" except when the word "educator" appears in the title.
--"or" expands the search.
eg. "music" or "teacher" finds all titles containing either the word "music" or the word "teacher."