Today it is possible to search for two words. Could be : fruit apples

As the system is now, all pages containing fruit OR apples will be shown

In many cases users want to find pages where both words appears.

Could be done by : fruit + apples  or   fruit & apples.

This should mean that only pages containing BOTH words were shown in the search-result. 

Another ( maybe better )  solution could be, that when You have the search-results-page, when using the search field on that page, only made a search in the found pages. In this way You could refine Your search until You find what You search for. If You want to make a new search You must use the search field outside the search-result-window. This will give a wery flexible combination of OR and AND searches with one or more words. The search in the results give the AND effect, and the search function itself is the OR function.