An exothermic change or reaction is one in which heat energy is given out to the surroundings. The surroundings get warmer, so the temperature of the reaction mixture rises.
Examples include burning fuels, which is called combustion, neutralisation reactions between acids and alkalis, and many oxidation reactions. Displacement reactions such as zinc with copper(II) sulfate solution are also exothermic. Some salts dissolving in water are exothermic as well, such as anhydrous copper(II) sulfate.
Everyday uses of exothermic reactions include hand warmers, self-heating cans and burning fuels for heating and cooking. In all of these, the useful effect is that heat energy is given out.