It is a 20-point inspection which includes checking the pressures, the refrigerant, and the thermostat. He will make sure there is no obstructions in the blower or the vents. He will ensure everything is working properly for the upcoming season. If he does see anything that will be a possible issue in the near future, he will let you know and give you a quote on how much it will cost to take care of it early therefor potentially saving a lot of money for emergency repair down the road.