Great question! The air fry feature uses hot air for crispier and healthier frozen or fresh foods with less (or no) oil than normal convection modes. For best results, use this mode in single oven mode. The convection feature uses a fan in the back of the oven cavity circulates the hot air evenly throughout the oven cavity. As a result, foods are evenly cooked and browned in less time than with regular heat. Convection can be used in single or twin mode. ^Jecca