The difference between an exothermic and an endothermic reaction lies in the energy exchange with the surroundings. In an exothermic reaction, energy is released, usually in the form of heat, as reactants transform into products. This process increases the temperature of the surroundings and is characteristic of combustion and respiration reactions. Conversely, an endothermic reaction absorbs energy from the environment, resulting in a decrease in temperature. Photosynthesis is a prime example, as it requires energy input from sunlight to convert carbon dioxide and water into glucose and oxygen. Understanding these reactions is crucial in energy transformations.