A CE router ( customer edge router ) is a router located on the customer premises that provides an Ethernet interface between the customer's LAN and the provider's core network. CE routers, P (provider) routers and PE (provider edge) routers are components in an MPLS (multiprotocol label switching) architecture. Provider routers are located in the core of the provider or carrier's network. Provider edge routers sit at the edge of the network. CE routers connect to PE routers and PE routers connect to other PE routers over P routers.
Here's one scenario: A customer who has facilities in LA and Atlanta wants to connect these sites over an MPLS VPN provided by AT&T. To do this, the customer would purchase a link from the on-site CE router to the PE router in AT&T's central office and would also do the same thing in LA and in Atlanta. The PE routers would connect over AT&T's backbone routers (P routers) to enable the two CE routers in LA and Atlanta to communicate over the MPLS network.