LOL...explosiveness. Click the link below Cbonez...
Or keep reading if you want the short version.
Octane is a comparison rating. The easiest way to explain it is that fuel with an octane rating of 87 is 87% as resistive to autoignition as pure octane. Fuel that has a rating past 100 is better at resisting autoignition than octane.
The whole point is that the lower the octane rating, the more likely you will get ignition during compression. As the piston rises, the air/fuel mix in the chamber compresses and the air temperature rises. Fuel with a low octane rating will autoignite before the spark ignites it. This is what creates "knock" in an engine and wastes fuel and power. The only vehicles that see a benefit with higher octane fuel are vehicles with high compression engines (sports cars, some aircraft).