[chuck-users] => now

Hi, I'm trying to understand what's really happening in chuck. I thought i did untill i saw some exemples of midi. Normaly you can only feed time or duration into now ( e.g. 10::ms => now) But in case you are awaiting a midi-in message you write : MidiIn min; while (true) { min => now } So in fact do you assign the message to time? Total confusion! Thanks for your answer. Herman