What is a condenser in air conditioning?

Pretty simple, it condenses the refridgerant into a liquid (giving off energy as heat) the cooling happens later in the evaporator part where the liquid turns back into a gas (taking the energy from surrounding area, thus lowering the temperature.) The condenser turns the refrigerant into a liquid by lowering the volume it is occupying, tightening up the molecules forcing the refrigerant into a liquid state.