Hi guys, could you explain this code to me please.

xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
{
document.getElementById("myDiv").innerHTML=xmlhttp.responseText;
}
}

if it xmlhttp.onreadystatechange equals the result of the function than why is there no return? am i on the right track or completely off?

Thanks