can some one explain what the following lines do

[adi5402]

I need help understand the following pieces of code im still new to php so my knowlage is limited.

piece 1

header ("Refresh: 5; URL=" . $_POST['redirect'] . "");
          echo "You are being redirected to your login area!</br>";
          echo "(If your browser doesn't support this, <a href=\"" .
               $_POST['redirect']. "\">click here</a>)";

piece 2

else 
{
if($_SERVER['HTTP_REFERRER'] =="" || $_SERVER['HTTP_REFERRER'] =="http:/localhost/index.php")
{
$redirect ="index.php";
}
else
{
$redirect =$_GET['redirect'];
}
?> 

[drawmack]

<?php
//here we are sending out a meta header to the page
//that will cause the page to redirect in 5 seconds.
header ("Refresh: 5; URL=" . $_POST['redirect'] . "");

//then here we output to the user that they are being
//directed to the login area and provide them with a 
//link to that area in case the header refresh doesn't work.
echo "You are being redirected to your login area!</br>";
echo "(If your browser doesn't support this, <a href=\"" .
$_POST['redirect']. "\">click here</a>)";
?>

<?php
else {
    //here we check to see if they came from our index page
    //or got here without the referer being set somehow
    //it they have we set $redirect to our index page
    //otherwise we set $Redirect to a variable provided in
    //the url called redirect.
    if($_SERVER['HTTP_REFERRER'] =="" || $_SERVER['HTTP_REFERRER'] =="http:/localhost/index.php") {
        $redirect ="index.php";
    } else {
        $redirect =$_GET['redirect'];
    } //end if
?>