i have always wondered, and so i just looked it up. here's an explaination of a few of the wierd movie terms/
"The key grip is head of the grip department on a movie set. He and his assistants are technicians and handymen (the hammers) who work for the director of photography, making sure the cameras are rigged properly and setting up nonelectrical light devices - the flags, nets and other props that control shadows. A dolly grip moves the camera along the dolly.
In his pamphlet listing the duties of the film crafts, William E. Hines says a grip's duties include ''loading, unloading, placement and trimming of all grip equipment (century stands, flags, gobos, scrims, screens, cukes, cutters, cycloramas, backings, backdrops, etc.).'' Is that perfectly clear?
In some cases, grips also heft around scenery. ''The grips are the cowboys,'' says Lynda Obst, associate producer of ''Flashdance.'' ''They are the ones who carry the heavy load of the schedule. They are the existential heroes of the set, the leaders of the crew. The speed of the work is very dependent on the key grip.''
Now, the key grip works with the gaffer, who also has a first assistant called the best boy. A gaffer is the chief electrician and he, too, reports to the director of photography. His job is to command a crew of riggers and juicers (electrician's helpers), who set up and control the lights - no small responsibility in an industry that depends above all on light.
''What the grip is to shadow, the gaffer is to light,'' explains Tony Marra, the key grip. Jim Grce is a gaffer, and, unlike the average electrician, he sees his work as art. He works with the cameramen to create an image."
Cliff notes: a grip does whatever teh fuck the people making the movie tell them to.