Final answer:
An exothermic reaction releases energy, most commonly in the form of heat.
Step-by-step explanation:
An exothermic reaction is a chemical reaction that releases energy, most commonly in the form of heat. During an exothermic reaction, the bonds in the products have higher bond energy than the reactants.
The energy given off is usually in the form of heat, although a few reactions release energy as light. In exothermic reactions, heat flows from the system to its surroundings, causing the surroundings to get warm.