Skin Friction Drag is the drag due to the friction between the air and the surface moving through the air. The friction is experienced because your hand tends to try to pull the air along with it. A wing can have the same drag as a wire that is much smaller than the wing. The difference is that the wing has mostly skin friction drag, and the wire has mostly pressure drag. These two shapes have the same overall drag Another kind of pressure drag occurs at the tips of the wings.
Air always wants to move from high pressure to low pressure.
These vortices have a lot of kinetic energy. The engines have to produce extra power to overcome the energy that these vortices create. Because these vortices make the engines work harder, impede the motion of the plane, and are caused by the lift, they are often referred to as drag due to lift. These wingtip vortices are the main reason that planes must wait a while between takeoffs. It can be dangerous flying in the vortices of another plane.