Grilling and barbecuing are often mistaken for each other. They are two different techniques. Grilling cooks food over a high heat to seal in the flavors. Barbecuing cooks food over a low and indirect heat, using the smoke to cook, as well as flavor the food.
The temperature for grilling is 425° to over 500°, where as barbecuing is done between 180° to 240°. When grilling make sure the fire is not too hot or you will torch the outside of your food before the inside has had a chance to cook.
With barbecuing make sure that your cooking vessel is pretty well sealed and then vented to optimize your cooking times. Barbecuing cooks the food slow and if done right can add tons of flavor to your meat or fish.
There are many different methods people swear by to make the best barbecue. Just remember that your grill needs to have varying temperatures so you can move things around, some hot spots and some cooler spots.