Okay so if you don't use types, wouldn't you would just be writing vanilla javascript and would have no reason to use typescript in the first place though?
It has a somewhat nicer syntax for functions and better scoping rules, but you could certainly get that from a more lightweight js extension like coffeescript yeah.
Not exactly, there is still type inference mechanism at work which, combined with DefinitelyTyped (https://github.com/borisyankov/DefinitelyTyped) declarations will get you quite a lot type safety even if you won't write any type declaration by yourself.