This feature on VirtualPBX work in a similar way in that you can assign any number of extensions to a Ring Group and treat it like an extension itself. When a Ring Group is prompted, be it in the Auto Attendant, through the Automated Directory, or any other method, all of the extensions in that group will ring simultaneously until a member of the group answers. Think of this as a way of allowing inbound callers to address a room full of your experts know that one of them will have a quick answer.
This feature is a great way to disperse callers to the right department, instead of having them be moved around to try and find the correct team member to speak to. This is only one of the many dynamic and innovative features provided by VirtualPBX.