MP3 - MPEG Audio Layer 3
MPEG Audio Layer 3, is an encoding format for digital audio which uses a form of lossy data compression, which means the original bits cannot be recreated from the compressed bits.
It can reduce the size of an audio file on the CD upto its 10th part. The most common bit rate for an MP3 file is approximately 256 kilobits per second which is roughly one-sixth of the 1.4 megabits per second required by the compact disc (CD) format.
As opposed to its reduced size, it still sounds like a faithful reproduction of the original audio to its listeners. It is due to the deficiency in human hearing system to throw away digital bits corresponding to sounds that cannot be heard.