All the & is is just additional parts to the QueryString in PHP ? is just signifies hey querystring and straight after we have the first get string to continue this on we use & an another variable string.
myindex.php?action=add&id=2
on myindex.php
echo $_GET['action']." ".$_GET['id'];
// output: add 2
Also to get them on you must do that within the address for the link, PHP wont add them in automatically but PHP will allow you to use the superglobals which are set automatically to retrieve them.
You may want to search to for QueryString to find similar threads on this topic also.