Here you can specify a list of words which each field must contain. To specify a phrase which must appear in the field surround your phrase with double quotes "". By adding a - before the word or phrase you can specify words or phrases to exclude from the search.
For example a search for "cambridge imaging" -systems, will search for the phrase "cambridge imaging" but without the word systems. To search for partial words you should use * as a wildcard. For example a search for 'system*' will result in hits for any word beginning with 'system'