Analog or analogue is a device that has continuously changing physical properties and values. Humans see the world around us analogically. There is a continuous stream or signal of information transmitting to our senses. Vision is an analog experience, as humans perceive many and varied smooth gradations of shapes and colors. These include audio and visual. Digital, in contrast, only estimates the analog data using ones and zeros.
A clock is a typical analog device. The hands move continuously around the clock face. This device is capable of indicating any possible time in the day. In contrast, digital clocks only represent a predetermined number of times.
Another example is the record player (or turntable). It is an analog device as it reads bumps and grooves from a record as a continuous signal (record the exact sound). Alternatively, a CD player is a digital device as it only reads a sequence of ones and zeros that simulate audio data (estimate the actual soundwave). The VCR is another analog device, as it reads audio and video as a continuous stream of information from a tape. The DVD player is digital as it again reads ones and zeros from a disc.
The reading of ones and zeros by digital devices can only estimate an audio or video signal. This would make analog data more accurate than digital; although, digital has the added ability to manipulate data easier and preserve it better. The other advantage is that computers are able to handle digital data and accordingly, the majority of information today is stored digitally.
By modulating the continuous transmission signal the data in analog format is transmitted. Telephones receive sound vibrations and then turn them into electrical vibrations of the same shape as when transmitted over the telephone lines. Radio waves work in a similar way. Traditional telephone lines can only carry analog signals.
Computers handle data in digital form. To receive or send signals by telephone lines, a computer requires a modem that can convert the signals from digital to analog and back again.