Energy content refers to the amount of energy stored in a substance, which can be released during a chemical reaction or physical process. It is commonly measured in units such as calories, joules, or kilojoules. Different materials, like fuels or food, have varying energy contents, influencing their efficiency and suitability for specific applications. Understanding energy content is crucial for various fields, including nutrition, where it helps determine the energy provided by different foods, and engineering, where it aids in selecting appropriate fuels for engines. Higher energy content typically means more energy can be extracted from a given amount of material.