"I need a medium shot for scene two take three from the D. to make sure the talent is ready and don't forget to check the lav mics in the audio booth." Many people may not have a clue as to what these statement means, but anyone in the movie business has to. The movie making industry has used all kinds of terminology over the years to describe their positions, their actions, and even pieces of equipment. People in the "biz" use these unique ways of speaking to ensure that everything is done quickly and efficiently. They need to do things this way for three basic reasons: Everything must get done in an exact way, things must also be done quickly, and anyone working on a movie set or TV show needs precise and distinctive terms to describe all the important things they have to do.
If a director said to a camera operator that he didn't know what kind of shot he wanted for a certain scene or a lighting director couldn't figure out how to make the lights work with whatever cameras they were using things might get a little out of hand. Anyone in that type of position has to know exactly what they want and how to tell someone, like a camera operator, how to do it. If they don't things probably won't get done the right way. A good lighting director should know that in small rooms where an interview may be taking place with a single camera, a three point lighting set up would be optimal. This kind of set up takes only three lights; a key light, a fill light, and a back light. Even then the job isn't done. Anyone setting up these lights also has to know what kind of creative atmosphere the director is looking for so he or she knows if they needs to use soft lights, a scoop light, or even colored gels to put on the lights that give a different effect. Usually people working on movies or a television show have a deadline so things must get done in whatever specific way the producers and director want them.