Refers to a person who cooks professionally, typically in a restaurant or commercial kitchen. More formal than コック and less specific than シェフ.
He is a chef at a first-class hotel.
To gain experience as a cook, I started working at a small restaurant.
Compound of 調理 (cooking) and 人 (person). The exact historical derivation is uncertain, but the word follows a common pattern for occupational nouns.