This helps to prevent the browser to use the cached version of file.
This help you to make instant changes (JS/CSS/Images (soon) to your website without need to clear the cache of OPcache/ NGinix / Browser / Joomla *
* If you want to have always updated timestamp order the system plugin AFTER the cache plugin, else need to clear the J! Cache
Replaces the domain from URLs if are internal and ingores the external links
Debug Report Example: