What is a Modem

ModemA Modem which comes from the word “Modulator/Demodulator” is a device that modulates outgoing digital signal from computer or any digital devices into an analog signal to transmit trough cable or telephone lines and demodulates incoming analog signal from cable or telephones lines into digital signal to be used for any digital devices such as computer
In its basic explanation, a modem is a device that allows you to send and receive information with your computer through phone lines. You could send photos to your friends and receive e-mail messages from your family.

Modems are generally classified by the amount of data they can send in a given time, normally measured in bits per second, or "bps". They can also be classified by Baud, the number of distinct symbols transmitted per second; these numbers are directly connected, but not necessarily in linear fashion.

Faster modems are used by Internet users every day, notably cable modems and ADSL modems. In telecommunications, "radio modems" transmit repeating frames of data at very high data rates over microwave radio links. Some microwave modems transmit more than a hundred million bits per second. Optical modems transmit data over optical fibers. Most intercontinental data links now use optical modems transmitting over undersea optical fibers. Optical modems routinely have data rates in excess of a billion (1x109) bits per second. One kilobit per second (kbit/s or kb/s or kbps) as used in this article means 1000 bits per second and not 1024 bits per second.