An exothermic reaction is a chemical process that releases energy, usually in the form of heat. This means that during the reaction, the surrounding environment becomes warmer as energy is transferred from the reacting substances to their surroundings. Common examples of exothermic reactions include combustion, such as burning wood or fossil fuels, and the reaction of acids with bases. In addition to heat, exothermic reactions can also produce light, sound, or other forms of energy. The energy released can be harnessed for various applications, such as in batteries or explosives. Understanding exothermic reactions is essential in fields like chemistry and engineering.