If you don't have any understand of just how much is involved with being and NFL head coach then it's doubtful that I can explain it.
He manages the team. That involves everything from player discipline to travel schedule changes like the one last week. He is the primary decision maker on who starts and plays, who is inactive and he is the pivot point between the front office and the assistant coaches on adding/cutting players. He generally calls the timeouts during games, decides on whether to go for on 4th down, challenges calls by the refs, decides that McFadden will get 29 carries to only 5 for C-Mike, etc..
I don't know how my original reply didn't answer the question. He does what many Head Coaches in the NFL do including Jimmy who won Super Bowls in the same role.