In physics, energy is a fundamental concept that describes the ability of a system to do work or cause change. It's not something you can touch or see directly, but rather a property of objects and systems that allows them to interact with each other. Energy exists in various forms and can be transformed from one form to another but cannot be created or destroyed—this is known as the law of conservation of energy. Energy has many forms. Some of these include chemical, potential, nuclear, and kinetic.

Energy is not a physical property of a system but simply a value assigned to a system that can be used to relate a system at 2 different points in time or configuration. Energy is a scalar and measured in Joules (J).