Understanding a WordPress Plugin

<?php
/*
Plugin Name: Yet Another Search Meddle
Plugin URI:
Version: 0.1
Author: Jeffrin Jose T and Public Domain
Author URI: http://linkedin.com/in/jeffrinl
Description: modifying the way search results are displayed

*/

function resultsperpage($limits) {
/* resultsperpage - it is a custom created php function. */

if (is_search()) {
/* is_search() - it is an inbuilt php function in wordpress */
/* http://codex.wordpress.org/Function_Reference/is_search */

return 'LIMIT 0, 25';
}
return $limits;
}

add_filter('post_limits', 'resultsperpage');
/* post_limits - a wordpress hook ( a filter hook ) */
/* http://codex.wordpress.org/Plugin_API/Filter_Reference/post_limits */

/* add_filter - Hook a function to a specific filter action. */
/* http://codex.wordpress.org/Function_Reference/add_filter */