An appetizer is meant to stimulate your appetite, making you extra hungry for your main meal. It is part of a meal and is served before the main course. When dinner guests first arrive you might serve them brie with cranberries baked in puff pastry, deviled eggs with king crab meat and wasabi. In fact it can be anything you want it to be. The key here is that it is a very, very small portion.
There are many restaurants that specialize in only serving small plates, which are the portion size of an appetizer and can be hot or cold. When entertaining, serving a well planned appetizer can serve two roles. It gives you, as the host, time to finish up the main meal and any sides that you are serving. And it also allows your guests relax prior to eating.
