Apache handlers tell the server how to deal with web files that need to be processed on the server. For example, is set up to process files with .php extensions using . However, if for some reason you also wanted to process files with .phtml extension using PHP, then you would have to set up a custom Apache handler for your site. Note: People often get confused as to the difference between MIME types and Apache handlers. Basically, MIME types tell your browser how to handle files, while Apache handlers tell the server how to handle files.