There is a link, More Search Options, on the search form that allows you to fine tune your search. Each search option asks if your choice is an "absolute requirement" or not.

What does this mean? It simply means that if you select more than one option, and you answer no to "absolute requirement", then any profile that matches any of your criteria will be shown to you.

But if let's say you make one of the requirements absolute, then profiles that do not match that requirement exactly would not be shown. This will be the case even if there are profiles that match all your other requirements, but do not match one absolute requirement.