One of the most basic differences between mono and stereo is that mono involves the routing of audio signals through only a single channel, whereas stereo involves the routing of audio signals through two or more channels. By using more than one channel, stereo gives spatial information to the listener so that he can tell which direction the sound is actually coming from. This depth and direction perception created by stereo creates a real world or same room experience where the sound is originating from for the listener.
Mono is short for monaural or monophonic sound, whereas stereo is short for stereophonic sound.
Stereo sound sounds far more natural than mono sound. As a result, the sound experience delivered by stereo is considered to be of much more quality and sound really natural, which is why it is given more preference than mono sound in most situations.
The biggest plus point for mono sound is that it can be recorded without much hassle. Unfortunately, the same cannot be said for recording sound in stereo. Since only one channel is required to record mono sound, only one microphone is need, while no additional equipment is needed. Recording a sound in stereo is not only more experience because of the greater number of channels that it requires, it also needed additional equipment, which is used to splice the music channels together and create a single sound.
The simplicity of recording and delivering mono sound makes it a preferred choice in situations where creating depth and adding spatial information to sound is not of great advance and instead only ends up taking more bandwidth. It is for this very reason that voice communication, especially via phone, involves mono sound, using only one channel to route sound and deliver it to the other end.
Stereo sound is the preferred choice when quality sound is the requirement. Music and films typically give preference to stereo sound over mono sound. Additional channels makes it possible for the listener to clearly hear the different instruments used in the music, while the spatial information of the sound makes the film experience even more satisfying and realistic.