MP3 is the name of the file extension and also the common name of the type of file for MPEG-1 audio layer 3. Today, it is a common audio format for consumer audio streaming and storage, and the standard for the transfer and playback of music on most digital audio players. Because MP3 files are small, they can easily be transferred across the Internet.
MPEG Audio Layer 3
Layer 3 is one of three coding schemes (layer 1, layer 2 and layer 3) for the compression of audio signals. Layer 3 uses perceptual audio coding and psychoacoustic compression to remove all superfluous information (more specifically, the redundant and irrelevant parts of a sound signal. The stuff the human ear doesn’t hear anyway). It also adds a MDCT (Modified Discrete Cosine Transform) that implements a filter bank, increasing the frequency resolution 18 times higher than that of layer 2.
The result in real terms is layer 3 shrinks the original sound data from a CD (with a bit rate of 1411.2 kilobits per one second of stereo music) by a factor of 12 (down to 112-128kbps) without sacrificing sound quality.
Why is MP3 so Popular?
MP3 was designed by Moving Picture Experts Group and MP3s started appearing online in the 1990’s. The music format became popular, quickly, because compression allowed the file to be as little as 1/10th of the original size. Remember, in the 1990’s disk drives and storage space on consumer PCs was expensive.