Taking your WAV file example:
A WAV file will have a header, which specifies key information to a player or audio processor about the number of channels, sample rate, bit depth, length of data etc. After the header comes the raw bit pattern, which stores the audio samples (I'm assuming you know what sampling is - if not, see Wikipedia). Each sample is made up of a number of bytes (specified in the header) and specifies the amplitude of the waveform at any given point in time. Each sample could be stored in signed or unsigned form (also specified in the header).
