Modem
From Wikipedia, a free encyclopedia written in simple English for easy reading.
Modem stands for modulator - demodulator. A modem is considered both a input and output device. It is used to send information from one personal computer to another personal computer.
Modulation converts digital information (data) in your personal computer to analog information (audio tones).
Demodulation is the process of converting the analog information (audio tones) that is sent over the phone lines to digital information (data).
Pieces of information (data) are sent from one modem to another modem at a predetermined rate (called the baud rate).