Definition of a Redox Reaction
A redox reaction, also known as an oxidation-reduction reaction, is a chemical reaction in which there is a transfer of electrons between reactants. This reaction involves the oxidation of one reactant and the reduction of another reactant.

Transfer of Electrons
In a redox reaction, one reactant loses electrons, which is known as oxidation, while another reactant gains those electrons, known as reduction. The reactant that loses electrons is called the reducing agent, while the reactant that gains electrons is called the oxidizing agent. The transfer of electrons from one reactant to another results in a change in the oxidation states of the elements involved.

Example of a Redox Reaction
One common example of a redox reaction is the reaction between iron and oxygen to form iron(III) oxide, commonly known as rust. In this reaction, iron undergoes oxidation by losing electrons to oxygen, which in turn undergoes reduction by gaining those electrons.

Fe(s) + O2(g) → Fe2O3(s)

Here, iron is oxidized from an oxidation state of 0 to +3, while oxygen is reduced from an oxidation state of 0 to -2. The transfer of electrons between the reactants defines this reaction as a redox reaction.

Significance of Redox Reactions
Redox reactions are essential in various biological and chemical processes. They play a vital role in energy production, such as in cellular respiration, where electrons are transferred from glucose to oxygen. Redox reactions also occur in batteries, where the transfer of electrons generates electrical energy.

Conclusion
In summary, a redox reaction is a chemical reaction involving the transfer of electrons between reactants. This transfer of electrons leads to a change in the oxidation states of the elements involved. It is important to understand redox reactions as they are fundamental in various chemical and biological processes.