Whether you call it aircon, air con, portable cooling or portable air conditioning then it all works in the same way.  An air conditioning unit is very simple and in operation is similar to a refrigerator.

The hot air from the room is passed over a cold coil that makes it colder and removes some of the moisture that makes the air feel sticky.

This cooler air is blown back into the room to provide a fresh feeling.  

Air from the room is blown over the coil that is now hot to discharge this heat to the outside via the flexible hose.  

To make the air conditioning unit work efficiently it is essential that the hose discharges the hot air to the outside and not back within the room.  To help the air conditioning unit work as hard as possible keep the room well sealed closing doors and windows wherever you can.  Blinds will reduce the amount of heat coming in through windows.

Wall mounted systems like the Prem-I-Air PMINI range have the advantage of not having a hose to discharge air from the room to outside as they wall mounted straight onto the wall and discharge and draw fresh air in through two vents.  This type of unit is also suitable for use as a heater in winter. 

We are often asked for an air conditioner without a hose to outside, for something that can just stand on its own.  All air conditioners need to have some sort of connection to outside.  Either a hose through a window or a wall, an umbilical pipe (about 2" squashed diameter) through a window or wall or a straight connection through the wall for a fixed unit.  All of these options are to make sure that the hot air is being exhausted outside.

The only units that do not have an exhaust to outside are the air coolers.  They use a water soaked pad to cool the air, but they must stand in front of an open window with a door or window open on the opposite side of the room.  The fresh air coming in through the window passes over the pad and picks up the moisture.  Air coolers are fine as long as the windows are open and the air is dry.  As soon as the air becomes humid (or sticky) their cooling power is reduced because they cannot absorb as much moisture from the pad.  Keeping a through breeze will avoid this issue.