diff between mysql_escape_string and mysql_real_escape_string

$item = "Zak's Laptop";
$a=mysql_connect('localhost','root','');
//$escaped_item = mysql_escape_string($item);
$escaped_item = mysql_real_escape_string($item);
echo $escaped_item;

?>
output :  Zak\'s Laptop
See the code above we use the server connection, in case of using the mysql_real_escape_string,
if you are not mention the server connection
i.e $a=mysql_connect('localhost','root','');
you may get the error below
Warning: mysql_real_escape_string(): Access denied for user 'ODBC'@'localhost' (using password: NO) in c:\program files\easyphp1-8\www\currentworking\bikes_adda\mysql.php on line 5

Warning: mysql_real_escape_string(): A link to the server could not be established in c:\program files\easyphp1-8\www\currentworking\bikes_adda\mysql.php on line 5

so before using  mysql_real_escape_string , use server connection.
BUT In case of mysql_escape_string , we noneed to use of server conncetion.
 just use the code normally...

$item = "Zak's Laptop";
$escaped_item = mysql_escape_string($item);
echo $escaped_item;
?>
output :  Zak\'s Laptop

Note: mysql_escape_string() does not escape % and _.