ɡrip/
verb
-
take and keep a firm hold of; grasp tightly.
In essence, this is what grip is all about.
On big movie sets, labor is divided up into different departments. The Cinematographer (also known as the Director of Photography) is in charge of the camera department, the gaffer department, and the grip department.
The camera people run cameras.
The gaffers run the lights themselves – they deal with electricity and wattages and math.
The grip department sets up all the non-electrical equipment that supports the camera and lighting departments. They’re a team of people that has many duties — most of which involve putting things in places in three dimensional space and making sure they stay there securely.