The modem> is a device that allows your PC to "talk" over the telephone lines to other computers. The computer at the other end also has a modem so that it can receive what you PC sends. Modems come in two flavors: internal> and external>.

An internal modem is an expansion card> that plugs into an expansion slot> on your motherboard. Since it lives inside your PC it is called internal. Although this modem does not physically connect to a serial port> it does use one.

An external modem is a stand-alone or separate device that connects to your PC through a serial port. Since it sits outside your PC it is called external. These modems are more expensive than internal modems, but can easily be moved from one machine to another.

Each modem has telephone jacks in the back of them. You connect a telephone cord from the modem to your phone outlet and your PC is ready to go.