Can someone explain detonation vs pre ingintion

when i said crappy fuel i meant fuel that doesn't have high enough octane (not old gas)
When you compress anything even air you create heat. If you have low octane fuel it ignites easier. So putting low octane fuel in a high compression engine isnt good because the fuel lights on its own when it isnt suppose too.

Ok. Good info. News to me that lower octane fuel ignites easier than high octane. Good to know.