A cable modem is a hardware device that allows your computer to communicate with an Internet service provider over a landline connection. It converts an analog signal to a digital signal for the purpose of granting access to broadband Internet. A cable modem works by connecting a coaxial cable and then a Cat 5 (Ethernet) cord from the modem to a computer or network router. Network routers share your Internet connection between multiple computers. More modern cable modems may have the router built-in with the ability to share the connection over Wi-Fi.
The picture is a stand alone Motorola cable modem, there are also all-in-one modems with a modem and router in one box. If your modem only has one coaxial cable connection and one Cat 5 connection, your modem is a stand alone modem and needs a router to share the connection.
Cable offers a significant speed increase in Internet performance compared to a dial-up connection and is one of the fastest broadband solutions. Comcast and Time Warner are examples of cable Internet providers in the United States.
If the cable modem or Internet is not working, unplug the cable modem power cable, wait a few seconds, and plug it back in to reset the modem.