I believe we have a hub that answers this question but:
infrared gas grills pressurize gas in the housing of the burner and have ceramic-tile tops with thousands of ports. Convection barbecue burners (use air to conduct heat), also called "blue-flame" burners normally have 30 - 75 ports where the gas comes through the burner and ignites.
The infrared burner will create a thousand degrees at the cooking surface within a minute of igniting. Within 3 minutes most infrared grills are radiating over 1300 degrees focused at the grilling surface. When food is cooked with direct heat (like the sun on your skin on a hot day as opposed to the hot air surrounding you) the outer layer of the food is "seared". Searing the outer layer of your food stops any moisture from passing through the sealed barrier.
This means the moisture in the food is locked inside the food.
I have grilled T-bone steaks well-done, brow all the way through. When I cut the filet and the strip off the bone the plate filled up to overflowing with moisture. All that flavor is locked ini the food.
Infrared is really perfect for steaks but it is also great with almost all seafood, vegetables and a lot of fruits. Grilled fruits!