What is a router and a modem?

If you’ve been on the Internet for a while, you’ve no doubt heard the terms “modem” and “router” thrown around, but might not have taken the time to understand what they are. We’re here to help.

In short, your router creates a network between the computers in your home, while your modem connects that network—and thus the computers on it—to the internet. When you connect to Wi-Fi, you’re really connecting to your router, which forwards traffic between the internet and your computer. Many internet providers offer a combined modem/router unit that performs both these functions in one device.

So why bother to understand the difference? Because that understanding can lead to better decisions, like buying your own modem so you can stop paying $8-$15 a month to rent one from your ISP.

A router connects multiple networks and routes network traffic between them. It’s really that simple. In the case of your home network, your router has one connection to the Internet and one connection to your private local network. In addition, most routers also contain built-in switches that let you connect multiple wired devices. Many also contain wireless radios that let you connect Wi-Fi devices.

The simple way to think about routers—especially on your home network—is like this. The router sits in between your Internet connection and your local network. It lets you connect multiple devices to the Internet through one physical Internet connection and also lets those devices communicate with one another over the local network. In addition, the router offers some protection to your devices over being exposed directly to the Internet. To the Internet, all the traffic coming from your house looks like it’s coming from a single device. The router keeps track of what traffic goes to which actual device on your network.But you can’t connect directly to the Internet with just a router. Instead, your router must be plugged into a device that can transmit your digital traffic over whatever type of Internet connection you have. And that device is a modem.

What a Modem Does

Your modem serves as a bridge between your local network and the Internet. Historically, the term “modem” is shorthand for modulator-demodulator. Modems were used to modulate the signals on telephone lines so that digital information could be encoded and transmitted over them and then demodulated—and decoded—on the other end. Though more modern broadband connections—like cable and satellite—don’t really work the same way, we kept using the term “modem” because it’s a device people were already familiar with and associated with connecting to the Internet.

How a modem attaches to your network depends on the type of connection you have. The modem plugs into whatever type of infrastructure you have—cable, telephone, satellite, or fiber—and gives you a standard Ethernet cable output that you can plug into any router (or a single computer) and get an Internet connection.