A reaction in which oxidation and reduction take place simultaneously is called [[1]] reaction

A redox reaction is defined as a reaction in which oxidation and reduction take place simultaneously. 

 For example in the reaction of copper oxide and hydrogen

        CuO + H_2​  $\to$Cu + H_2​O

1. Removal of oxygen from Copper oxide to form copper (reduction)
2. Addition of oxygen to hydrogen to form water. (oxidation)