Difference between Oxidation and Reduction

Electron transfer reactions are called oxidation reduction reactions or reactions involving transfer of negative charge (ie. electrons) from one reactant to another. Oxidation and reduction are complementary processes. See the figure for better understanding.

In the above reaction, Sodium (Na) metal is the reducing agent as it supplies electrons for the reduction of chlorine and chlorine is the oxidizing agent as its accepts electrons form sodium thereby sodium gets oxidized.

Oxidation vs Reduction

Oxidation  (with respect to A)	Reduction  (with respect to A)
Oxidation is the loss of electrons or hydrogen atoms or gain of oxygen atoms.	Reduction is the gain of electrons or hydrogen atoms or loss of oxygen atoms.
Removal or loss of electrons A ->A++e-	Addition or gain of electrons A +e- -> A-
Removal of Hydrogen AH+B -> A+BH	Addition of Hydrogen A+BH ->AH+B
Addition of oxygen A+BO -> AO+B	Removal of oxygen AO+B -> A+BO
All the above reactions releases energy	All the above reactions stores energy

Examples of oxidation reduction reactions are corrosion, respiration, the operation of battery etc.