Grilling means
broiling food with direct heat.
[USA] Grilled food is usually cooked on a gridiron or a metal plate with flame applied from below.
[NON=USA] Outside USA, the term refers to a cooking directly under a source of direct, dry heat.
grillers are usually a separate part of an oven where the food is inserted just under the element. The door of a griller is normally left open during cooking to increase dryness.