Firstly, it is spelt "chef de cuisine".
In the brigade system invented by Escoffier, the chef de cuisine is the head chef, creates the menus, supervises everyone else, and in a large kitchen, probably does very little actual cooking because they're managing the whole operation. The buck stops here! They may be running the pass - the place where all food has to come to for the waiters to pick it up from, and maybe he or she will want to be there especially if there are new chefs, just to look at each plate as it goes out and be satisfied it's right. Orders also come in at the pass.
In a large kitchen, under the chef de cuisine there will be sous chefs to run a part of the kitchen, chefs de partie responsible for individual dishes, and at the bottom of the pecking order, commis chefs to prepare and chop ingredients.
