Router
A router is a device that connects two or more packet-switched networks or subnetworks.
t serves two primary functions: managing traffic between these networks by forwarding data packets to their intended IP addresses, and allowing multiple devices to use the same Internet connection.
There are several types of routers, most pass data between WAN and LAN networks.
How does a router work?
Think of a router as an air traffic controller and data packets as aircraft headed to different airports (or networks)
In order to direct packets effectively, a router uses an internal routing table — a list of paths to various network destinations. The router reads a packet’s header to determine where it is going, then consults the routing table to figure out the most efficient path to that destination. It then forwards the packet to the next network in the path.
Difference between router and modem?
Although some Internet service providers (ISPs) may combine a router and a modem within a single device, they are not the same. Each plays a different but equally important role in connecting networks to each other and to the Internet.
A router forms networks and manages the flow of data within and between those networks, while a modem connects those networks to the Internet. Modems forge a connection to the Internet by converting signals from an ISP into a digital signal that can be interpreted by any connected device. A single device may plug into a modem in order to connect to the Internet; alternately, a router can help distribute this signal to multiple devices within an established network, allowing all of them to connect to the Internet simultaneously.
Think of it like this: If Bob has a router, but no modem, he will be able to create a LAN and send data between the devices on that network. However, he will not be able to connect that network to the Internet. Alice, on the other hand, has a modem, but no router. She will be able to connect a single device to the Internet (for example, her work laptop), but cannot distribute that Internet connection to multiple devices (say, her laptop and her smartphone). Carol, meanwhile, has a router and a modem. Using both devices, she can form a LAN with her desktop computer, tablet, and smartphone and connect them all to the Internet at the same time.