Detonation is a knocking noise that you'll hear coming from your engine. It's caused by the air/fuel mixture in the cylinders igniting too early. This can damage your engine over time, so it's important to be able to identify it and fix the problem.
There are a few ways to tell if you're experiencing detonation. The first is by listening to your engine. If you hear a knocking noise, that's a good indication that something isn't right. Another way to tell is by looking at your spark plugs. If they're black and sooty, that's another sign of detonation.
If you think you might be experiencing detonation, the best thing to do is take your car to a mechanic and have them check it out. They'll be able to diagnose the problem and recommend a course of action for fixing it.