What does a Key Grip on a film do?

As Marvel takes over Hollywood and its domain, it is becoming increasingly common to see people sticking around in theaters through the end of a film's credits. Of the weirdly-named jobs on a movie, Key Grip was one that stood out to me. So what do they do? Turns out, they're not holding the keys to anything.

Here's the answer from Wikipedia: 

Before filming begins, the key grip attends location scouts and meets the Director of Photography to determine what additional tools (location-specific motor vehicles, dollies, cranes, mounts, etc.) will be needed, orders and preps required equipment, and transports equipment to the filming location.^[2] Once on set, the key grip coordinates with the electric and camera departments alongside the Director of Photography to control lighting and camera movement and setup.^[3] As a supervisor, the key grip directs the crew of grips, many with specialized skills such as dolly grips, crane operators, or special equipment operators.^[2] The key grip is sometimes credited as the "first company grip."^[4]