The inbuild/default wordpress search box allows you to search within the posts module and show the results on search pages which generally are called using the searchresults.php file but in case you have a website with huge amount of pages, comments and want the visitors to search everything rather than just the posts then you should try out this wordpress plugin named as ‘Search Everything‘

Search Everything increases the ability of the default Wordpress Search, options included. Features of Search Everything :

* Search Every Page
* Search Every Tag
* Search Every Category
* Search non-password protected pages only
* Search Every Comment
* Search only approved comments
* Search Every Draft
* Search Every Excerpt
* Search Every Attachment
* Search Every Custom Field (metadata)
* Exclude Posts from search
* Exclude Categories from search