If a GoodSync client can connect to GoodSync server directly (by TCP/IP) then you will obtain the maximum speed of transfer.
However this may be not possible for a personal computer that accesses the Internet from behind NAT, firewall, or security software.
So when the GoodSync client cannot connect to a GoodSync server, they try to arrange a meeting via a go-between server that we call Forwarder. The Forwarder is accessible from both client and server. The Forwarder is appointed dynamically, based on the visibility of client and server.
This is an automatic process requiring no user intervention.
The Forwarder does not store any data in transit and is only used to facilitate the connection between source and destination.