Refer to figure.
Airplanes’ piston engines are reciprocating engines, similar to your car’s engine, with the difference that they use special aviation fuel to run. However, a failure of an airplane engine due to fuel issues can be potentially fatal, so safety dictates that aviation fuel must conform to very stringent requirements. It is made of various selected grades of gasoline, combined to give high anti-knock ratings. The octane rating of a fuel indicates its resistance to detonation. The use of too low octane gasoline in a piston engine will increase the chances of detonation. However, using fuel with a higher-octane grade is perfectly normal provided it is designed to take advantage of a higher-grade fuel.

For your general knowledge, the octane rating is based on the knock resistance difference between two spirits, iso-octane (which is very good) and heptane (very poor). By degrading iso-octane with heptane until the blend detonated in a variable compression engine under the same standard conditions as the fuel under test, it was possible to classify that fuel by a number representing the percentage of iso-octane in the test mixture. In this way, 89-octane fuel corresponded to a mixture of 89% iso-octane and 11% heptane.