It includes an architecture and a set of protocols for routing over a provider's network, allowing interconnection of multiple provider bridge networks without losing each customer's individually defined VLANs.
QinQ does not offer true separation of customer and provider domains but is merely a way to overcome the limitations on the VLAN identifier space.
The idea of PBB is to offer complete separation of customer and provider domains.
The bridges in the PBB domain switch based on the B-VID and B-DA values, which contain 60 bits total.
Bridges learn based on the B-SA and ingress port value and hence is completely unaware of the customer MAC addresses.