Endothermic reaction

 An endothermic reaction is a reaction that takes energy in from its surroundings causing the temperature of the reaction surroundings to decrease. 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 happen. A common way for energy to be supplied is by heating the reaction mixture. 

The opposite of an endothermic reaction is an exothermic reaction.