Combustion is the burning of compounds in air to give ${CO}_2$ and water with the liberation of heat and light.
Oxidation is the reaction in which carbon compounds take up oxygen in the presence of oxidizing agents to give another carbon compound.
Thus, All combustion reactions are also oxidation reactions but oxidation reactions are not combustion reactions.
In fact, Combustion means complete oxidation.
For Example —
Combustion :
1. Carbon compounds on combustion (complete oxidation) give ${CO}_2$ and ${H}_2 {O}$.
$$\text { Oxidation; } {CH}_2 \longrightarrow {O}_2 \longrightarrow {CO}_2({g})+2 {H}_2 {O}({g})$$
2. Alcohols are oxidised to acids in the presence of alkaline potassium permanganate or acidified potassium dichromate.
$${CH}_3 {CH}_2 {OH} \stackrel{{O}}{\longrightarrow} {CH}_3 {COOH}$$
3. With cold dilute alkaline potassium permanganate, ethene (ethylene) is oxidised to ethylene glycol.
$${CH}_2={CH}_2 \stackrel{{O}+{H}_2 {O}}{\longrightarrow} {CH}_2 {OH}+{CH}_2 {OH}$$
