Search Modes There are four basic modes that are available.
“Find all my search terms” is the default mode. In this search, words entered in a single text box are automatically linked by the Boolean style “AND.” This means that the search engine makes sure that all of them are present in the results that it has. Where the word appears in the same area (for example in the title, or the subject, etc.), depends on which types of search you are doing.
“Boolean/Phrase” should be used when you need to do any detailed Boolean searching or exact phrase searching. "Stopwords" (which are words that turn up in all records, such as "the" and "a") are ignored when part of phrases being searched.
“Find any of my search terms” – Auto "OR" all search terms entered (e.g. web OR accessibility). This means that within a given text string, the search engine with make sure to find at least one of the words there.
“SmartText Searching” is an interesting option. This search requires you to enter (or copy/paste) a text string of up to 5000 characters (which is between 1-2 pages of single-spaced text). The search engine then ranks the words in the text (depending on things like how often the word shows up), and gives results that are based on what it determined the page was about.