Both use direct heat. No pan stands between the food and the heat source. That's what you call it when sugars and proteins react to give the rich flavors of browned foods. The whole idea of broiling is speed. Get the broiler really hot, put the food under it very briefly, whip it back out before it burns.
Professional kitchens have a piece of equipment called a salamander.
Salamanders get very hot, concentrating a lot of heat on a small area, like a plate of food. The broiler in a home electric oven doesn't get nearly so hot. You just don't have as much heat as you really want. Then switch the oven to broil, give it a few minutes to preheat, and put the food under it. You want the heat to attack the food.