A reaction in which an acid and base react with each other to give a salt and water is termed as neutralization reaction. In this reaction, energy is evolved in the form of heat. For example :

$(i)$ $\underset{(Base)}{\mathop{NaOH}}\,\,+\,\underset{(Acid)}{\mathop{HCl}}\,\,\to \,\underset{(salt)}{\mathop{NaCl\,}}\,+\,\underset{(water)}{\mathop{{{H}_{2}}O}}\,$

$(ii)$ During indigestion (caused due to the production of excess of hydrochloric acid in the stomach), we administer an antacid (generally milk of magnesia, $Mg(OH)_{2}$, which is basic in nature). The antacid neutralizes the excess of acids and thus gives relief from indigestion.

$Mg ( OH )_{2}+2 HCl \rightarrow MgCl _{2}+2 H _{2} O$