As the Concorde flies at supersonic speeds, the center of lift shifts towards the back of the plane, making the nose heavy and the plane unbalanced. To keep the plane balanced as it accelerates during flight, fuel is moved from the front to the rear. Transferring the fuel shifts the center of gravity. By adjusting the center of gravity at the same time as the center of lift shifts, the plane remains balanced. During supersonic flight, center of lift shifts back.
Fuel is transferred back to shift the center of gravity and balance the aircraft.
During deceleration, center of lift shifts forward. Fuel is transferred forward to shift the center of gravity and balance the aircraft.