According to Wikipedia a CHEF is a professional cook, who may work in a restaurant, hotel, institutional food service or other professional kitchen.  The term origionally referred to the rank of head cook, but has become generalized to any trained, professional cook.  With that being said what do you call the at home cook?  Oddly enough I couldn't find anything on that besides the lable of an "at home cook"... 

The info below came from Wikipedia...

Various chef titles

Below is a non-exhaustive list of various titles given to those working in a professional kitchen and each can be considered a title for a type of chef. Many of the titles are based on the brigade system documented by Georges Auguste Escoffier, while others have a more general meaning depending on the kitchen in which one works. Not all restaurants will use these titles as each establishment may have its own set guidelines to organization.

Executive chef

The executive chef is in charge of everything related to the kitchen, including menu creation, staff management and business aspects. While the position requires extensive cooking experience and often involves actively cooking, it is not necessarily very hands-on. They can also be referred to as the "chef" or even "head chef". Although "head chef" may seem redundant, the word "chef" has come to be applied to any cook, kitchen helper or a fast food operator, making the distinction necessary.

Chef de Cuisine

This is a synonym for the title executive chef. This is the traditional French phrase where the title chef comes from and is more common in European kitchens or American kitchens with a classical French brigade system. In some establishments this title is used to designate a chef who is the head chef at one location of an operation that has multiple locations where the corporate chef has the title executive chef.

Sous chef

The Sous Chef is the direct assistant of the executive chef and is second in command. He or she may be responsible for scheduling, filling in for the executive chef when he is off-duty. He or she also will fill in or assist the chef de partie (or line cooks) when needed. Smaller operations may not have a sous chef, while larger operations may have multiple.

Expediter or Announcer (Aboyeur)

The expediter takes the orders from the dining room and relays them to the stations in the kitchen. This person also often puts the finishing touches on the dish before it goes to the dining room. In some operations this task may be done by either the executive chef or the sous chef.

Chef de Partie

A chef de partie, also known as a "station chef" or "line cook", is in charge of a particular area of production. In large kitchens, each station chef might have several cooks and/or assistants. In most kitchens however, the station chef is the only worker in that department. Line cooks are often divided into a hierarchy of their own, starting with "First Cook", then "Second Cook", and so on as needed.

Station chef titles which are part of the brigade system include

Sauté Chef (Saucier) [so.si.e] - Responsible for all sautéed items and their sauce. This is usually the highest position of all the stations.

Fish Chef (Poissonier) [pwɑ.so.ɲe] - Prepares fish dishes and often does all fish butchering as well as appropriate sauce. This station may be combined with the saucier position.

Roast Chef (Rotisseur) [ʀo.ti.sœʀ] - Prepares roasted and braised meats and their appropriate sauce.

Grill Chef (Grillardin) [gʀi.ʎaʀ.dɛ̃] - Prepares all grilled foods, this position may be combined with the rotisseur.

Fry Chef (Friturier) [fʀi.ty.ʀje] - Prepares all fried items, position may be combined with the rotisseur position.

Vegetable Chef (Entremetier) [ã.tʀə.me.tje] - Prepares hot appetizers and often prepares the soups, vegetables, pastas and starches. In a full brigade system a potager would prepare soups and a legumier would prepare vegetables.

Roundsman (Tournant) [tuʀ.nã] - Also referred to as a swing cook, fills in as needed on station in kitchen.

Cold-Foods Chef (Garde Manger) [gaʀd mã.ʒe] - May also be referred to as the pantry chef, they are responsible for preparing cold foods, including salads, cold appetizers, pâtés and other charcuterie items.

Butcher (Boucher) [bu.ʃe] - Butchers meats, poultry and sometimes fish. May also be responsible for breading meats and fish.

Pastry Chef (Pâtissier) [pa.ti.sje] - Prepare baked goods, pastries and desserts. The pastry chef often supervises a separate team in their own kitchen or separate shop in larger operations. Some kitchens may have an executive pastry chef.

This station may be broken down into smaller areas of specialization -

Confiseur - Prepares candies, and petit fours.

Boulanger - Prepares unsweetened doughs for breads and rolls.

Glacier - Prepares frozen and cold desserts.

Décorateur - Prepares show pieces and specialty cakes.

Specialized and hierarchal chef titles are usually found only in fine-dining, upscale restaurants; kitchen staff members at casual restaurants such as diners may be called chefs but are more often called "cook" or "short-order cook." A chef may be referred to as a mere cook either to reflect a lack of formal training, a focus on "home" rather than fine-dining cuisine, or to imply amateur quality food.

This all came from Wikipedia btw...