If deferred = waitlisted, it means that the school has already sent out acceptance letters to enough people to fill its class, but depending on how many of those students accept (yield), they may accept people off the waitlist if they have room.
If they placed your application on 'hold,' it means that for whatever reason they need mor time to look at your application. This seems to be rarer than being waitlisted and I am not sure why a school would do this exactly, or how it differs from being placed on the waitlist, but the consensus out there seems to be that being placed on hold gives you better chances than being waitlisted. You could try and call the school to ask them.
Hope this helps, and good luck!