First, you use a deep fryer for deep frying and you use a skillet for pan frying. When deep frying, you use a lot of oil for cooking and you completely immerse the food in that oil. On the other hand, when pan frying in the skillet, you use a little oil on the surface area of the skillet. Also, a deep fryer does not expose food to air and that enhances quick cooking. On the other hand, when pan frying, the food is exposed to air, thus, taking much longer to cook.