A dining-hall is a large space where many people eat at the same time. If you go to college and live in a dormitory, you'll probably eat most of your meals in a dining-hall.
You can use the word dining-hall when you're talking about a cafeteria or another group space for eating. You'll find dining-halls at universities, camps. and boarding schools. The word hall. a long room, comes from the Old English root heall, "spacious roofed residence," and dining is rooted in the Old French disner, "to have a meal."