A condenser is the portion of an HVAC system or plant that releases heat from the refrigerant to the air, making the refrigerant condense from a gas into a liquid

This process heats the surface of the condenser and is the warm side of the refrigeration process. A condenser is typically outside (except in the case of a heat pump)

You can often identify a condenser by locating cooling towers or by locating a large set of fans on a unit outside.

In a home air conditioner, the condenser is the unit outside of the residence (except for heat pump systems)