What is the difference between airtight and open compressor?

An airtight compressor is used in small air conditioning installations and domestic refrigerators. Its main feature is that the engine is located together with the compressor in a housing where there is no room for maintenance. The oil stays in contact with the refrigerant and circulates throughout the system. In the open the motor and the compressor are separated and connected by an axis. Of course, maintenance is made easier.