What do you mean by oxidation and reduction reaction?

Solution

Oxidation can be defined as addition of oxygen or removal of hydrogen from a chemical substance. Conversely, reduction can be defined as the removal of oxygen or addition of hydrogen to a chemical substance. 

For example, consider the following reaction

In the above reaction, oxygen atoms are being added to copper. Thus, copper is getting oxidised in the above reaction.

Similarly, in the formation of MgO from Mg and oxygen, magnesium is being oxidised to magnesium oxide.

 2Mg + O₂ → 2MgO

Now, consider the following reaction

In the above reaction, copper oxide is losing oxygen. Thus, CuO is getting reduced to Cu.

Note: In higher grades, you will study that oxidation and reduction can be defined in terms of loss and gain of electrons. While oxidation is termed as loss of electrons, reduction can be defined as the gain of electrons.