Understanding WAV (Waveform Audio File Format)
WAV is a raw audio container format, developed by Microsoft and IBM. It is the standard for storing an audio bitstream on PCs.
Unlike MP3, which uses perceptual coding to discard "unimportant" sounds, WAV stores the audio as a series of values representing the air pressure at each moment. This is called Pulse Code Modulation (PCM).
When you convert MP3 to WAV, you are taking the approximated audio wave from the MP3 and "printing" it into a solid, uncompressed stream. This makes the file significantly larger, but easier for computers to process during editing.
