This is an amazing page by Bartosz Ciechanowski: a tutorial where you can drag things, rotate things and generally be interactive while learning how cameras work.
A great deal of labour must have gone into this, and it’s also a very impressive demo of what web browsers are capable of these days.
But if cameras aren’t your thing, don’t worry – Ciechanowski doesn’t stop there.
Well, you get the idea! Pretty impressive stuff.
Thanks to Michael Dales for the initial link.