This article has been updated to provide more information about routers and home networking.
You may often see references to computer-networking devices called routers, switches and hubs. All three connect multiple computing devices such as computers, printers and other networking equipment to one another, but each works differently and for different benefits and purposes.
Hubs are the simplest way to connect two or more computers, servers and peripherals to form a simple network. A hub receives signals from each machine though wired connections, and then broadcasts them to all the other connected machines. So if Computer A sends out a signal, Computers B, C and D will all receive it, even if the signal was meant only for Computer D.
Switches are more complicated in that, unlike hubs, they manage network traffic instead of just broadcasting signals.
Each message sent by a computer or peripheral will contain information about which computer it comes from, and which it's meant for, and the switch makes sure the message gets to the correct destination on the local network. If Computer A sends a message to Computer D, a switch will make sure that Computers B and C don't receive it.
Routers connect networks of computers, not computers themselves. Unlike switches, which forward messages only to known devices on a local network, routers can forward messages across the world to devices with which they’ve never before communicated.
Imagine a large company that has different computer networks for each department. If Computer A in Accounting wants to send a message to Computer B in Human Resources, the message may pass through a router that's connected to both the Accounting and Human Resources networks.
If there's no direct connection between the Accounting and Human Resources networks, then the router connected to the Accounting network will send the message to a second router, which may in turn send it to a third router, and so on, in order for the message to reach the Human Resources network.
The router connected to the Accounting network knows how to reach the Human Resources network by looking in its routing table, a list of available routes that can be used to reach specific networks.
Because of this intelligent routing, and the need to update and transmit routing information, routers are actually small computers with their own operating systems.
They constantly communicate with other routers, sharing information about traffic routes and network status among themselves, even as they handle network traffic between servers and end-user computers.
Think of a police officer directing traffic at a busy intersection. The cop is telling cars to stop, go, turn left or turn right, which is akin to regular network traffic. But at the same time, the cop is on the radio to other traffic cops, sharing information about which streets are jammed up and which have smoothly moving traffic. Routers do the same thing.
The small consumer-based wireless gateway routers used in millions of North American homes and small offices are actually fairly complex devices combining the features of switches, routers and wireless access points.
Acting like switches, wireless routers connect several wired computers, and other wired networked devices such as printers, in the same home or office to form local networks and to manage network traffic. Like routers, they connect the home network to the larger network of the home's Internet service provider (ISP).
Similar to wireless access points, wireless routers send and receive Wi-Fi radio signals from laptops, tablets, smartphones and other wireless devices, and translate the signals into standard wired network protocols before passing them on to the switching functions.
The Internet is a shared connection among of millions of routers, ranging from small home wireless routers to Border Gateway Protocol routers that link giant telecommunication companies. Each router on the Internet is theoretically able to reach any other router, even if the router sending the message isn’t sure whether the destination router exists. But that’s best left for another article.