A chef is a person who cooks professionally for other people. Although over time the term has come to describe any person who cooks for a living, traditionally it refers to a highly skilled professional who is proficient in all aspects of food preparation.
The word "chef" is borrowed (and shortened) from the French term chef de cuisine (French pronunciation: [ʃɛf.də.kɥi.zin]), the director or head of a kitchen. (The French word comes from Latin caput and is cognate with English "chief".) In English, the title "chef" in the culinary profession originated in the haute cuisine of the 19th century. Today it is often used to refer to any professional cook, regardless of rank, though in most classically defined kitchens, it refers to the head chef, others, in North American parlance, are 'cooks'.
Below are 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 de cuisine (or brigade system) documented by Auguste Escoffier, while others have a more general meaning depending on the individual kitchen.
Chef de cuisine, executive chef and head chef
This person is in charge of all things related to the kitchen, which usually includes menu creation, management of kitchen staff, ordering and purchasing of inventory, and plating design. Chef de cuisine is the traditional French term from which the English word chef is derived. Head chef is often used to designate someone with the same duties as an executive chef, but there is usually someone in charge of them, possibly making the larger executive decisions such as direction of menu, final authority in staff management decisions, etc. This is often the case for chefs with several restaurants.
The Sous-Chef de Cuisine (under-chef of the kitchen) is the second in command and direct assistant of the Chef. This person may be responsible for scheduling and substituting when the Chef is off-duty and will also fill in for or assist the Chef de Partie (line cook) when needed. This person is responsible for inventory, cleanliness of the kitchen, organization and constant training of all employees. The "Sous-Chef" is responsible for taking commands from the Chef and following through with them. The "Sous-Chef" is responsible for line checks and rotation of all product. Smaller operations may not have a sous-chef, while larger operations may have several.
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.