Using a gas grill is very different than using a charcoal grill. Gas grills use propane, butane or natural gas as their source of heat. Food cooks differently with gases than it does on charcoal or wood burning grills because of different temperature, different types of flames and some other contributing factors as well.
Some say that only charcoal grills make food taste right, but you can cook up a mean steak on a gas grill if you know what you're doing. It is important to know your grill, know your food and know how they are going to work together.