WAV and AIFF are essentially the same with the only real difference being the order of the bytes in a sample (little-endian vs big-endian). They are both just a sequence of PCM samples. WAV is predominant on Intel CPU based machines.
The samples on a CD are PCM but they are not in linear order as in a computer based format. When you rip a CD, the PCM samples are read, placed in order [left channel sample 1, right channel sample 1, left channel sample 2, right channel sample 2...] and the WAV header is calculated and prepended to the samples to form a file that is then saved with a .wav extension.