Analog may stand for “a person or an object which may be compared to another”.
An analogy is a comparison of two things that are similar.
An analog device uses information represented by a continuous variable.
An analog thermometer measures temperature via the expansion of the mercury in its bulb.
The analog speedometer displays the speed of a car via the needle on its dial.
Some early computers are analog (e.g. Differential Analyzer). The later computers are mostly digital. Some computer systems are hybrid.
There are tools to convert analog signals to digital, and vice versa.
ADC is a tool to convert Analog to Digital.
DAC is a tool to convert Digital to Analog.
The sounds produced by a musical instrument are analog.
Analog information may be digitized by using appropriate sampling techniques.