The JPagination class allows developers to reliably and consistently add pagination to the Front-end and Back-end display of their components. The file containing the class can be found at /libraries/joomla/html/pagination.php.

The construct function of the class requires three variables: $total - the total number of items in a list, $limitstart - the offset of the item at which to start, and $limit - the number of items to display per page.

In my case I wanted Pagination for the products. therefore in controller extend the joomla pagination class.

function product() { $limit = 20; $limitstart = JRequest::getVar('limitstart', 0, '', 'int');

$db=JFactory::getDBO();
$query_2 = 'SELECT * FROM #__rg_products';
$db->setQuery($query_2);
$detail = $db->loadAssoclist();   
jimport('joomla.html.pagination');
$pagination = new JPagination(count($detail), $limitstart, $limit); 

$query = "SELECT * FROM #__rg_products ORDER BY id LIMIT ".$limitstart.", ".$limit." ";
$db->setQuery( $query );
 $arrresult = $db->loadAssoclist();

$query_3 = "SELECT * FROM #__rg_categories WHERE level = '1' ; " ;
$db->setQuery($query_3);
$catresult = $db->loadAssoclist();

// echo"

"; print_r($catresult); exit;


$this->assignRef('catresult', $catresult);
$this->assignRef('arrresult', $arrresult);
$this->setLayout('product');
$this->assignRef('pagination', $pagination);
parent::display();

}


In our view.php we can use any of the 2 functions to display the pagination:
1.)  getPagesLinks(): Returns an HTML string to display the Pages Links as << Start Prev 1 2 Next End >>
2.) getListFooter(): Returns a combination of the several page-related elements, including: the Display Limit dropdown, the Pages Links and the Pages Counter. Appearance differs in the Front-end and Back-end due to additional CSS formatting applied with the Khepri template.

Make sure that these functions are inside the form in your file specifically when using for back-end, 
 pagination->getPagesLinks(); ?>