Difference Between Digital and Analog Signals?

A computer performs its tasks by turning on and off a series of electronic switches represented by the numerical digits of 0 and 1. A 0 is the code for off, and a 1 is the code for on. Combinations of these digital codes represent text, computer commands, and graphics inside the computer, By comparison, the telephone works by sending sounds in a continuous analog signal sent along an electronic current that varies in frequency and strength.