Routing Protocols and Concepts

The main purpose of a router is to connect multiple networks and forward packets destined for its own networks or other networks. A router is considered a Layer 3 device because its primary forwarding decision is based on the information in the Layer 3 IP packet, specifically the destination IP address. This is known as routing.
When a router receives a packet, it examines the destination IP address. If the packet does not belong to any of the router’s directly connected networks, the router must forward this packet to another router or drop the packet.
When forwarding a packet, the router will encapsulate the Layer 3 IP packet into the data portion of a Layer 2 data-link frame appropriate for the exit interface. The Layer 2 frame will then be encoded into the Layer 1 physical signals used to represent these bits over the physical link.
Knowing the functions of the main internal components of a router is more important than knowing the locations of the physical components inside a particular model. Therefore, in your own words, provide a sufficiently detailed description of each component.