When routing with the OSPF protocol, there are different routers with dedicated functions. These include the Designated Router( DR), the Area Border Router ( ABR) and the Autonomous System Boundary Router( ASBR).
The Area Border Router (ABR) is a router that connects one or more OSPF, Open Shortest Path First, areas to the backbone network. An ABR router has at least one interface in a routing area and one to the backbone network. ABR routers perform routing interface functions between a given area and the backbone area.