Most grills cook through convection (air is heated by a flame or burning charcoal and continually circulates around the food, thereby cooking it). Infrared primarily cooks through a process of radiation. Heat is radiated straight from stainless steel plates, sitting over a gas burner, to the food sitting above it. This process is much quicker and gets a great deal hotter than a regular gas burner. Most gas burners reach about 750° F, whereas an infrared burner can easily reach 900° F or hotter. For this reason, most grills with infrared technology will contain one or two infrared burners to give you an option of high-temperature grilling. A gas grill made up entirely of infrared burners would get much too hot for normal grilling practices.
