Moisture is "vented away".  No water is produced.  The moist air is vented to the outside or moved to another area that is ventilated. Most common installation.

Focussing the dry air gives faster drying times.  Example of "Positive Pressure" or forcing the dry air into areas it is needed

Recirculating the air to be dried gives a compound effect and gives faster drying.  This system is a "Negative Pressure" system.   Air has to replace the air that has been exhausted with the wet air.

15% of the air that is processed is expelled as wet air.  This air needs to be replaced.  Air from outside the room may be more humid.  This is averted with a larger model.

Having the machine in the area being dried and recirculating the air is the most efficient way of drying.  This system is "Negative Pressure. In a small enclosure, covered with plastic sheeting a frame is needed to ensure the tent maintains structure.  Rooms generally are not air tight so in larger rooms air can leak under doors etc

3-hole systems have one advantage over 4-Hole systems.  Around 60 Watts of energy will be retained in the process air flow with a 4-Hole system.  Normally this is not a problem (Same energy as an old home light bulb) but if it is a variable air valve may be added to balance the system with regen air. 

This assumes that the air from any variable inlet (variable in order to find balance of air flow) is colder than the air inside the room being dried.   Typical applications will include  buildings where heat generated by people is not covered fully by any air conditioning.