A modem is a device that connects your home or office to the internet. It converts digital data from your computer into a format that can be transmitted over telephone lines, cable systems, or satellite connections. This process is called modulation and demodulation, which is where the name "modem" comes from. Without a modem, your devices wouldn't be able to communicate with the internet. There are different types of modems, such as DSL modems, cable modems, and fiber-optic modems, each designed for specific types of internet connections. Many people use a combination of a modem and a router to create a wireless network, allowing multiple devices to connect to the internet simultaneously.