How this keyword works?

var foo = {
bar: function() { return this.baz; },
baz: 1
};
(function(){
return typeof arguments0;
})(foo.bar);

In the foo object when the bar function is called its, this is set to the object the method is called on.
This means that if we call foo.bar() we would get 1.

I am not able to understand the what this line -

return typeof arguments0;

does ?