Quote Originally Posted by Rynjin View Post
Boilers aren't actually the same thing as water heaters. Boilers can produce hot water but their primary purpose is for heating the building. And they will actually boil water until it turns to steam. It just cools to usable temperatures after making its way through a building.
That's at least correct for U.S. terminology (though I'd add that boilers aren't just for heating buildings, they're also really useful in chemical plants and the like to do temperature control for particular reactors, separators and the like), with a few other definitions of boilers floating around as well, e.g. steam engine boilers. For U.K. though that might be entirely different.

Where exactly this leaves U.S. boilers in U.K. terminology is an open question.