What are the parts of an auto ac system?

Depending on the system type -

A Freon gas - R134a (R12)

P.A.G Oil

High Pressure Pipes

Low pressure pipes

Compressor

Condenser + Condenser fan

Receiver/dryer - including a 'desiccant' type substance (Calcium oxide)

Expansion Valve or Orifice Tube

Evaporator

Geoff3bee