One of the best examples of an endothermic reaction is the chemical process of dissolving table salt in water. If you pour salt into a bowl or container of water, the salt will automatically dissolve on its own. This chemical process will lower the temperature of the water in the container, consuming some of the energy from the water. This process is called endothermic reaction and it is spontaneous in normal pressure and temperature.
An endothermic reaction happens when more energy is required to break or dissolve the bonds in the reactants than what is released when a product is formed by its new bond. To simplify, the endothermic reaction takes a certain portion of energy in order to work.