It was my understanding that Teredo is mainly used for Remote Assitance behind a NAT device.
But this goes into more detail about it..... Teredo tunneling - Wikipedia, the free encyclopedia Teredo
is a tunneling protocol
designed to grant IPv6
connectivity to nodes that are located behind IPv6-unaware NAT
More succinctly,, it means,,, "The idea was that the protocol (Teredo) would pierce holes through NAT devices"