Question: What is a modem?

Answer: A modem is a piece of hardware that allows your computer to talk to other devices over a regular phone line.

A modem converts digital signals from your computer into audible tones that can be transmitted over regular analog phone lines. This conversion process is called MOdulation. The modem on the other end then transfers those same audible tones back (or DEModulates) into their original digital signals.

MOdulation and DEModulation is where the name MODEM comes from.

There are basically two different types of modems (internal-inside of the computer and external-outside of the computer). Either type of modem works technically the same way. One computer sends the information digitally and then . . .

. . . the modem translates the digital signals into an analog signal. The analog signal is transfers over the phone wires. The modem at the other end translates the analog signal back into the original digital signal and sends that information to the computer.

There are actually signals going back and forth from the two computers to verify that all of the information is correct. Kind-of-like repeating everything to make sure that it is all heard correctly. The computers use a system of checksums to repeat the information to save time.

Question: What is an analog signal?

    Answer: Analog refers to adding signals to carrier waves, usually represented as sine waves. These signals are not simply on or off. It is similar to a dimmer on a light switch - not just on or off but many positions in between.
Question:What is a digital signals?

    Answer: Digital signals are either ON or OFF and no in between - JUST like a (regular) light switch for your room.
Question: What is a checksum?

    Answer: Checksums are kind-of-like me giving you 100 numbers and you telling me the total. If the total is correct, I assume that you heard all of the information correctly. It is a little more complicated than that - but that is basically how it works. It saves a considerable amount of time to verify information this way rather than repeating everything.
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