[jQuery] fn question

[David .Wu]

I found these both work, so what is return for?

<script>
$.fn.btnClick = function() {
        this.click(function() {
                alert('test');
        });
}

$('input#btn').btnClick();
</script>

<script>
$.fn.btnClick = function() {
        return this.click(function() {
                alert('test');
        });
}

$('input#btn').btnClick();
</script>