Earth is home to a multitude of energy transformations. Even in our daily lives, we continuously convert various forms of energy, guaranteeing ourselves a wide range of services. In its most basic definition, energy is a body’s ability to complete a job. The job is, in essence, the process of transferring or converting energy.
There are many forms of energy. Among the more important kinds are kinetic energy and potential energy. Kinetic energy is tied to the movement of a body, like the blade of a mill that moves when pushed by water or wind. Potential energy, on the other hand, is contained within a body, in repose, and can evolve based on its state or position, for example, its height above the ground, transforming into kinetic energy or other forms of energy. Mechanical energy is the sum of potential energy and kinetic energy, that is, energy associated with the movement and position of an object.
Our physical world contains many forms of energy, some of which are listed to the sides. The law of conservation of energy is valid for every type: energy neither creates nor destroys itself; it can transform itself from one form into another; it can move from one body to another, but its total quantity remains unchanged.

• IEA (International Energy Agency), World Energy Balances 2022