[Jack-Devel] Ports vs Channels in JACK

Hi, Simple question about JACK that I haven't been able to find anywhere else. Hoping someone here's kind enough to set me straight. :) Coming from PulseAudio, I noticed that JACK's documentation and discussions seem to barely mention things regarding channels....but do refer to ports quiet often. So I was wondering what kind of mapping there is between say L and R channels and JACK ports? Or does a mapping even exists? Thanks, Hai