In this chapter first we learn about classical idea of redox reactions – oxidation and reduction reactions. Then we study redox reaction in terms of electron transfer reactions including competitive electron transfer reactions. Then we know oxidation number, different type of redox reactions : combination reactions, decomposition reactions, displacement reactions, disproportionation reaction. Then we learn how to balance a redox reaction through oxidation number method and half reaction method. Then we know redox reaction as the basis for titrations and then limitation of concept of oxidation number. After that we discuss redox reactions and electrode processes.