Belgians typically eat three meals a day, with a light breakfast, light or medium sized lunch and large dinner.
As with many European countries, food is often heavily influences by neighboring countries (for Belgium, France and to a lesser extent Germany and the Netherlands), historical conquests and of course climate. Even in a reasonably small country such as Belgium there are regional differences and traditions.
A tradition in Brussels is to cook with local beers and great steaming pots of mussels are particularly favored. The Flemish share the Dutch fondness for raw herring, generally eaten with equally raw onions. The Belgians are famous for their fried potatoes (steak-frites).These are twice-fried potatoes and are best when topped with homemade mayonnaise.
Other well know Belgian specialties are chocolates, waffles and as mentioned earlier, beer.
For more information see Wikipedia.