Traffic engineering is a set of techniques to steer certain types of traffic via a path different from the IGP-calculated shortest path.
Egress Peer Engineering is a technique for ingress ASBR to steer traffic to the specific BGP peer of the specific egress ASBR.
In large networks, there might be a need to introduce some hierarchy in routing design, in order to reduce the amount of LSP flooding and prevent local routing instabilities from impacting the entire network.