The best way to visualize how the call forwarding and calling services is to consider the following video, which shows how call forwarding and call transfers can be combined to make complex rules such as Find-Me / Follow-Me and follow the type of intelligent sun routing calls.
In another basic example, we can consider that incoming calls are intercepted on some devices that host the actual destination numbers such as land land, which will then be transferred automatically to alternative numbers in this case on the SIM card on the cellphone. The way it will work is that the landline owner might want to come out so they have configured their home phone to direct all the calls to the number to be transferred or forwarded to their mobile alternative preset number. In this scenario all incoming calls will be transferred automatically and smooth without the caller even pay attention.
The important difference between call forwarding and calling calls is that the previous method to forward phone calls is usually based on semi-permanent on call routing devices such as personal telephone exchanges (PBX). While the difier call is done on the phone itself usually through short code and only based on needs.