It's a bunch of syntax sugar. The proposal is that instead of typing this:

    fn foo(b : bool) -> Result<Bar,Baz> {
        ...
        return Ok(bar);
        ...
        return Err(baz);
    }

you can type:

    fn foo() -> Bar throws Baz {
        ...
        return bar;
        ...
        throw baz; //or yeet, in this proposal
    }

and it works exactly identically as the first example. ? still works inside the function just as it normally would. I find the proposal sort of pointless, but also totally harmless, so why not.