Explanation:

The Boolean selection allows you to refine your search. The ‘AND’ option can be replaced with the ‘OR’ option, which is more general. For example, you can select ‘Inverter’ AND ‘Boat’, in that case only pages which have BOTH the words will be displayed. If the ‘OR’ option was selected then EITHER word would cause the page to be displayed.

Usually the case is left as insensitive, however if a particular word is known to be in CAPITALS, then this can assist a search.