Answer :
The reaction in which oxidation and reduction occurs simultaneously is known as Redox reaction. e.g. when Hydrogen gas is passed over heated copper oxide ,copper is obtained. In this reaction copper oxide get reduced by losing oxygen at the same time Hydrogen gets oxidised by gaing Oxygen, so this reaction can be called as oxidation-reduction or redox reaction. \( CuO + H_{2}\rightarrow Cu+H_{2}O\)