why we used Model

[eluser]BD-CI-Programmer[/eluser]
I am using a Controller like this

Code:

<?php
class Bangladesh extends Controller
{
    function Bangladesh ()
    {
        parent::Controller();
    }

function my_function()
{

$this->load->database();
$query = $this->db->query("Query")
if($query->num_rows()>0)
   {
return $query->result();
   }
else
return 0;

   }

}
?>

this code is working. But my questions, why we used Model