Explanation of this Code Please

Hi,

I am new to the Javascript could you please explain this 8 lines code for me Please.

<script type="text/javascript">
        $(".chk").live("click", function () {
            if ($(this).is(":checked")) {
                if (!$(this).closest("tr").next().hasClass("child")) {
                    $(this).closest("tr").after("<tr class = 'child'><td></td><td colspan = '999'>" + $(this).next().html() + "</td></tr>")
                    var index = $(this).next();
                    $(this).next().next().val(index);
                }
            } else {
                if ($(this).closest("tr").next().hasClass("child")) {
                    $(this).closest("tr").next().remove();
                }
            }
        });
    </script>