Energy is a tricky thing to define but after you read this you will understand it in an elementary level. Energy is disturbance, more accurately a disturbance in a medium. We will call a medium that exists in all the infinity of the universe a field. Fields are what gives particles their masses and charges. There are the two types of energy in the universe. For example lets think about kinetic energy, this is a type of energy due to the disturbance of a massive particle created by it's movement in space. When a particle with mass travels in space it creates a disturbance in the higgs field. With that you can confirm that temperature is a state of the kinetic energy. What about light? Well light is the disturbance created by the disturbance of the electromagnetic field in our universe, light it self is just a disturbance traveling at the speed of light without mass.
|Particle traveling in higgs field|