The basic idea behind cookies is very simple. The site stores a little bit of info on the users computer, which can be accessed at a later point in time. The info stored can be anything, but usually consists of the users username, password, etc. for that particular site.
Any questions/comments, please feel free to contact me.
// basic syntax
setcookie("stuff to store", $variable, "expiration date");
//example, expires 1 year after the cookie is stored
setcookie("stuff", $var1, time()+31104000);
//to retrieve cookie
$var1 = $_COOKIE['var1'];