Routers connect two or more logical subnets, which do not necessarily map one-to-one to the physical interfaces of the router.[1] The term layer 3 switch often is used interchangeably with router, but switch is really a general term without a rigorous technical definition. In marketing usage, it is generally optimized for Ethernet LAN interfaces and may not have other physical interface types.

Routers operate in two different planes [2]:
Control Plane, in which the router learns the outgoing interface that is most appropriate for forwarding specific packets to specific destinations,
Forwarding Plane, which is responsible for the actual process of sending a packet received on a logical interface to an outbound logical interface