What is the difference between exothermic and endothermic reactions?

The first law of thermodynamics states that energy can neither be created nor destroyed. Energy has to be used when breaking bonds, yet is formed when making bonds. This means that there will be an overall net release of energy to the surroundings or removal of energy from the surroundings. If the energy required to break bonds is greater than that which is formed when making bonds, the reaction is endothermic and takes in energy from the surroundings. However, if the energy required to break the bonds is less than that which is formed when making bonds, the reaction is exothermic and releases energy (in the form of heat - thermal energy) to the surroundings.