What are Ring Groups?
The Ring Groups Module is used to create a single extension number that your users can dial in order to ring multiple extensions at the same time. It also creates a destination to which you can send calls that will ring those multiple extensions.
For example, you could create a Ring Group that will allow your local phones to dial 600, and then all (or some) of the phones in the office will ring. You could also set the Ring Group as a destination in an Inbound Route, so that calls to a DID (i.e., a phone number) specified in the Inbound Route will cause all of the Extensions in the Ring Group to ring when the DID is called. You could also set the Ring Group as a destination an an IVR, so that when a caller presses 1, a group of phones will ring.