Analog: The key to the analog signal is that it is continuous. In another word, the wave slowly raises peaks, gradually descends, bottoms out and gradually climbs again. Taken as a simple illustration, imagine numerous forms of wave signal. Some of the waves are closer altogether than others, some might have more height; still others might really begin their peaks and descents in completely different positions! Encoding data can be completed based on such different types of wave changes.
One of the noteworthy considerations in analog communications is the capability to decode such continuous wave forms. With the prologue of noise, or other signal disturbance, decoding an analog signal properly can be hard. This is why we turn into the digital communications system.