At its highest point (Point A) the pendulum is momentarily motionless. All of the energy in the pendulum is gravitational potential energy and there is no kinetic energy. At the lowest point (Point D) the pendulum has its greatest speed. All of the energy in the pendulum is kinetic energy and there is no gravitational potential energy. However, the total energy is constant as a function of time.
Your hand is the pivot or the fulcrum. It is where the pendulum swings from. The string is the lever; it holds the weight and undergoes tension forces. The stone is the load. It can be put to some certain height and cause the swinging
