Everywhere around us we see movement and action. For example, people walk, elevator rise , football is kicked ,cars move etc .None of these actions are possible without energy.in science,these movement and actions are called work. This, we define energy as
The ability to do work.
However working here does not mean just sitting and thinking. It means to create a movement or a change . Although energy is necessary to do work ,it's presence does not mean it is capable of doing work. The energy which is present but us not doing work is know as stored energy.
For example a petrol in a car cannot work until the engine is not in working condition.
Similarly energy present in us cannot b utilized until we move. When we move we are said to do work .all living and non living things need energy to do work.Living thing need food and non living things need other forms of energy like heat light,sound etc
Energy and it's firm are measureable .
Therefore energy is a physical quantity.