Who talks to who?

So continuing from my last post my last week here is what I picked up on set. Grips are your equipment people they set up the equipment such as set pieces and things of that nature and they talk only to the key grip or best boy if there is one on set. Best boy is like the second in command of the grips. Then you have the gaffer who is in charge of the lights who then has a best boy also sometimes. Who uses the grips so the though they do not talk to him. Then you have the DP (director of photography) that talks to the directors and so does the AD (assistant director) are really the only people that should talk to the director beside obviously the actors. The DP then talk to the Key Grip, and the Gaffer and work collaboratively to get the setting done. That is what I get from sets usually.