PCM the "normal" way to store audio, where the height of the wave is sampled at x times per second and represented by an x-bit number. And DMC (DPCM) the way a NES stores audio, which is something like the gradient of the wave stored as a 1-bit number (either "up" or "down"), I think.
You'd have to have dmc files if you wanted to use them in famitracker (well I think famitracker has its own converter but this one is definitely better), ppmck, etc.