A dining facility in large institution like a school, office, camp, hospital etc. where the members of that institution come to eat, although public cafeterias exist, mostly as a cheap dining option. Cafeterias usually consist of a serving counter or counters along one wall near the entrance where one pushes along a tray and is served portions of food by the staff. The rest of the room usually consists of seating often consisting of large multi-seat tables. The cafeteria fare generally consists of a few set meals of an entree and various side dishes to complement that entree, often there is a flat fee for a meal, although one is charged for extra portions or optional dishes like deserts. Another common price scheme is each dish has it's own price and a customer chooses which dishes to purchase. Commonly a cafeteria will have a main line (or lines) consisting of a hot meal at a flat price and an a la cart line consisting of individually priced dishes like salads and sandwiches.  It's probably noisy, and the food probably sucks. A cliche is the school cafeteria being segregated according to group membership, e.g. cool kids, outcasts, nerds, jocks, etc...  
食堂