```
var a = function(param1) {
    var b = function(param2) {
        console.log(param1 + param2);
    }; 
    return b;
};

a(4)(5); // this logs "9"

```

Is the return statement (in this case "return b") always necessary? Why do we need it for one function here, but not the other? When is it necessary, and why?