Shell & Tube Type Condenser is used to condense the vapor emerges out during the operation. It mainly works through condensing the vapors flow through tubes where they are treated with cooling water over external surface.
A condenser is a device that converts vapor into the liquid state whereas a heat exchanger is a device that is used for heat recovery also to transfer heat from two fluids. Heat exchanger only heat is transferred without phase change and heat is transferred along with the phase change in the condenser.
There are three types of condensers: air-cooled, water-cooled and evaporative.
Heat is transferred via solid material (conduction), liquids and gases (convection), and electromagnetic waves (radiation). Heat is usually transferred in a combination of these three types and seldomly occurs on its own.