Endothermic reaction
An endothermic reaction is a reaction that takes energy in from its environment, causing the surrounding temperature to reduce. This reaction occurs when the energy used to break the existing bonds in the reactants is greater than the energy used to create new bonds in the products[1]. This happens because the products of the reaction require more energy than the reactants so there must be a positive enthalpy change for the reaction to occur. A common way for energy to be supplied is by heating the reaction mixture.
The opposite of an endothermic reaction is an exothermic reaction[2].