1. A router is used to connect two or more networks while a modem is used to connect to a phone line.
2. A router only connects to RJ45 connectors while modems need an RJ45 and an RJ11 for the phone line.
3. A router provides security measures to protect your network but a modem does not.
4. A modem is essential to connect to the internet while a router isn’t.
Your router essentially shares your Internet connection among multiple devices. A typical router is now a wireless router, and it creates and hosts a Wi-Fi network multiple devices can connect to. It likely has multiple Ethernet ports, too, allowing you to connect multiple devices.The router then connects to the Internet through the modem and the router itself receives a single public IP address on the Internet. Servers on the Internet communicate with your router, and the router routes that traffic to the appropriate devices on your home network.But, with just a router, you can’t actually connect to the Internet. The router must be plugged into the Internet via an Ethernet cable. You need a modem to do so.

What a Modem does your modem communicates with your Internet service provider’s network. If it’s a cable modem, it plugs into your cable provider’s infrastructure via a coaxial cable. If it’s a DSL modem, it plugs into your telephone line.The modem communicates with your Internet service provider, and you’ll need the correct type of modem that will work with your ISP’s infrastructure. 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.