C4H8 + 6O2 --> 4CO2 + 4H2O
In first reaction, the C and H is oxidised (4 C gain 8 oxygen, 4 H gain 4 oxygen) while the O molecule is reduced
Redox is a reaction where oxidation and reduction happen simultaneously
In every reaction where there is oxidation, reduction reaction will also occurs.
These kind of reactions is called redox reaction