All this does is show the person on the site what their IP address is, it's not extremely useful, but it's extremely easy and comes in handy if you're logging each visitor! you can tell them their IP address and then tell them their being logged, that's just a security feature to not get hacked, or at least try to scare them off.
<?php
$ip = $_SERVER['REMOTE_ADDR'];
echo "Your IP address is as follows: " . $ip;
?>