In chemistry, redox reactions are also known as oxidation-reduction reactions. These types of reactions are classified by the transfer of electrons between species in the reactions. Typically, redox reactions occur when one chemical species is reduced while the other chemical species in the reaction is oxidized.
The term reduction refers to the gain of electrons while the term oxidation refers to the loss of electrons. In redox reactions, two half reactions are put together to make one whole reaction. When placed together, electrons can be transferred from one chemical species to another to complete the oxidation and reduction of the chemical species.