Air Conditioning - Portable Reverse Cycle Ducting Question

I am new to Air Condtioners and Heat pumps. We are looking at purchasing a portable reverse cycle air con unit to mainly heat one room.
I understand the unit has an air exhaust hose that needs to vent to the outside when used to cool the air. (exhausting hot air outside)
What happens in the process when we are trying to heat the air? (do we need to have the exhaust hose outside? or is it ok to leave it insiide behind the unit? Will the air that is exhausted be hot or cold?)
Sorry for the noobish questions, but it is going to be very convenient for us to have a heat pump for our situation and more so if we don't have to vent the exhaust air outside when using it to heat the air.

Thanks.
Tulip.

I've not worked with a "reverse cycle" portable. I would imagine that during cooling the condenser would be exausted to the outdoors and in heating mode the evaporater would be exausted outdoors. If it is a true portable heat pump it will do it all on it's own.