PHP What the meaning or use of echo << JS "some javascript code " JS;?

Question

I need to know what is the actual use or the need to write a echo like below,

echo <<< JS

                <script type="text/javascript" language="javascript">      
                        function writeThisStatus (obj,id) {
                              writeStatus(obj,id,'OPTUS_COMP');
                              setBackground('row_'+id,(obj.checked ? 1 : 0));
                        }
                </script>

JS; 

is this just equal to the normal echo " string "; or does something else ?