functions.php

<?php


function be_portfolio_post_class( $classes ) {
	<!-- I dont understand this part-->
	global $wp_query;
	if( !$wp_query-&gt;is_main_query() ) 
		return $classes;
<!-- End-->
		
	$columns = 3;
	<!-- I dont understand this part-->
	$column_classes = array( '', '', 'one-half', 'one-third', 'one-fourth', 'one-fifth', 'one-sixth' );
	$classes[] = $column_classes[$columns];
	if( 0 == $wp_query-&gt;current_post % $columns )
		$classes[] = 'first';
		
	return $classes;
<!-- End-->
}
add_filter( 'post_class', 'be_portfolio_post_class' );