Energy is the ability to do work and there are many types of energy.
Mechanical Energy is the energy of motion that does the work like the wind turns a windmill.
In physics, mechanical energy is the sum of potential energy and kinetic energy present in the components of a mechanical system. It is the energy associated with the motion and position of an object. The law of conservation of energy states that in an isolated system that is only subject to conservative forces, like the gravitational force, the mechanical energy is constant. If an object is moved in the opposite direction of a conservative net force, the potential energy will increase and if the speed (not the velocity) of the object is changed, the kinetic energy of the object is changed as well. In all real systems, however, non-conservative forces, like frictional forces, will be present, but often they are of negligible values and the mechanical energy's being constant can therefore be a useful approximation. Inelastic collisions, the mechanical energy is conserved but in inelastic collisions, some mechanical energy is converted into heat. The equivalence between lost mechanical energy and an increase in temperature was discovered by James Prescott Joule.
Many modern devices, such as the electric motor or the steam engine, are used today to convert mechanical energy into other forms of energy, e.g. electrical energy, or to convert other forms of energy, like heat, into mechanical energy.
Heat Energy where motion or rise in temperature is caused by heat like a fire in your fireplace.
In physics, chemistry, engineering, and thermodynamics, a quantity of heat is an amount of energy produced or transferred from one body, region of space, set of components, or thermodynamic system to another in any way other than as work.[1][2][3][4][5][6]This definition is the carefully developed fruit of the finding from experiments in physics that in general a definite statement cannot be