Trinary wiring

I'm working through getting my KW A model A/C updated to a Vintage Air unit and I want to make sure I understand the trinary wiring so I'm going to ask some dumb questions. The wiring diagram is the picture below. Tell me if I'm understanding this right:
Terminal 1 - This wire goes to the compressor to supply power to it.
Terminal 2 - Is this the wire coming from my unit in the cab that is for sending power out to the A/C compressor?
Terminal 3 - This one goes to the solenoid that turns my fan clutch on, correct?
Terminal 4 - Some sort of power source that is hot with the key on.
Thanks for helping the noob here.