Air flow and preheating mostly. Air fryers generally use higher temperatures as well. The big thing is moving Air helps transfer heat more effectively. If you don’t preheat an oven you get soggy stuff because it’s not hot enough to get the maillard reaction, before the surface gets waterlogged. An air fryer can preheat In a couple minutes, so there’s less time to get soggy, and the fab helps a bit too with evaporation.