Here's a breakdown:

* Knocking: This is the undesirable phenomenon that occurs in an internal combustion engine when the air-fuel mixture ignites prematurely before the spark plug fires. It creates a sharp, metallic knocking sound and can damage the engine.

* Antiknock Properties: Fuels with good antiknock properties resist knocking and allow for higher compression ratios in the engine.

* Octane Number: This number is a measure of a fuel's resistance to knocking. It's determined by comparing the fuel's knock resistance to a reference fuel. Higher octane numbers indicate better antiknock properties.

There are two main octane ratings:

* Research Octane Number (RON): Measured under controlled laboratory conditions.

* Motor Octane Number (MON): Measured under more demanding engine conditions.

The average of RON and MON is usually reported as the "pump octane" number you see at the gas station.

In summary:

* Octane number is the measure of antiknock properties in fuel.

* Higher octane number means better resistance to knocking.

* Pump octane is the average of RON and MON.

It's important to note that using a higher octane fuel than your engine requires provides no benefit, and in some cases can actually cause problems. Consult your car's owner's manual to determine the appropriate octane for your vehicle.