English Other Sports / Fitness / Recreation

Hello everyone,

From the book 99 Stories of the Game by Wayne Gretzky:

It happens in part because no one knows exactly what makes hockey hockey. It’s not just the rules. Those change. It’s not the equipment. God knows, everything is a lot different today. (But it is fun to imagine Bobby Hull stepping into a slap shot with one of the composite sticks Shea Weber uses, or a speed demon like Howie Morenz wearing ultra-lightweight custom Bauers like Taylor Hall’s.) What makes hockey the greatest game on the planet is something else. Something you can’t quite put your finger on. ***Coaches and GMs*** would be invincible if they knew exactly what makes a team more than just names on a roster. But even the Scotty Bowmans and Pat Quinns had their share of losses. The fact is, greatness is not captured in statistics. It’s captured in stories.

Do I understand correctly that GM stands for a general manager?
If yes, what's the difference between a coach and a general manager then?

I know that, for example, Sir Alex Ferguson is often referred to as manager of Manchester United, so if coach=(general) manager, why say "coaches and GMs"?

Thank you.