A Joule is a unit of energy in the International System of Units (SI). It is defined as the amount of energy transferred when a force of one newton moves an object one meter. Joules can also be used to measure heat, work, and electricity, making it a versatile unit in physics and engineering. In practical terms, one Joule is equivalent to the energy required to lift a small apple (about 100 grams) one meter against the force of gravity. Understanding Joules helps in various fields, including mechanics, thermodynamics, and electrical engineering.