Thrust is the force that moves an aircraft through the air. In a conventional fixed-wing aircraft, thrust provided by the propeller moves the plane forward while the wings supply the lift. In a helicopter both thrust and lift are supplied by the main rotor blades. Drag is the force of resistance by the air to the passage of an aircraft through it. Thrust force sets an aircraft in motion and keeps it in motion against drag force.
Any device designed to produce lift or thrust when passed through air is an airfoil.
Chord is the distance, or imaginary line, between the leading and the trailing edge of an airfoil. The amount of curve, or departure of the airfoil surface from the chord line, is known as the camber. If the surface is flat, the camber is zero. As air speed increases, surface air pressure decreases accordingly. This is directly related to the flight of an aircraft.