In physics, drag (sometimes called resistance) is a force which tends to slow down the movement of an object through a liquid or gas. As a moving object pushes the liquid or gas out of its way, the liquid or gas pushes back on the object. This drag force is always opposite to the object's motion, and unlike friction between solid surfaces, the drag force increases as the object moves faster.
Air resistance (drag) is a force that is caused by air, the force acts in the opposite direction to an object moving through the air. It is where air particles hit the front of the object slowing it down. The more surface area the more air particles hit it. For example a truck with a flat front will experience high air resistance while a sports car with a streamlined shape will experience lower air resistance, allowing the car to go faster.