Search – what are the rules?

Is there any place that actually describes how the standard search facility works? I gather it searches on words, but what about when you want a phrase?

For example, if I search HMAS AUSTRALIA (two words separated by a space) it gives me 208 posts with either the word HMAS or the word AUSTRALIA. But what if I want just the posts with the phrase HMAS AUSTRALIA?

Heaven forbid if I search “HMAS AUSTRALIA” – that yields “\\\ hmas australia\\\”. If I search HMAS+AUSTRALIA, I get “hmas+australia” but no posts returned.

I’m half expecting someone to tell me to use a Regular Expression, but since when would that be practical for users?

Is this all written down somewhere?
Will the standard search facility do phrases? If not, can anyone recommend a “proper” search plugin?

Ted