Router
In plain terms
A device that forwards data between different networks.
Going deeper
A router directs packets between networks, choosing paths toward their destination based on IP addresses and routing tables. It connects networks together.
Under the hood
Operates at layer 3, maintaining routing tables and running protocols like BGP/OSPF; home routers also do NAT/DHCP.
Examples
Home internet, BGP, packet forwarding, inter-network routing, gateways.
Think of it like...
Like a postal sorting hub deciding which route each package takes toward its city.