Here are some things that famous scientists and engineers have said, or found out, about energy...
ENERGY CANNOT BE CREATED NOR DESTROYED
ENERGY IS CONSTANTLY BEING TRANSFORMED FROM ONE FORM INTO ANOTHER EG. Light into Heat or Electricity into Sound etc.
ENERGY IS SIMPLY THE ABILITY TO DO WORK SUCH AS MOVING AN OBJECT OVER A CERTAIN DISTANCE
ENERGY AND MASS ARE RELATED BY THE EQUATION E=MC2