Sommeliers are professional wine stewards who are responsible for selecting, storing, and serving wines. They are knowledgeable about the history, production, and characteristics of different wines, and can advise customers on which wines to choose. Stewards are responsible for maintaining the quality of the wines they serve, as well as ensuring that the wines are stored properly. They also provide advice on food and wine pairings, and may be involved in the purchasing and inventory of wines.