Differents between petrol diesel engine?

Differents between petrol diesel engine?
Petrol engines are known as Spark ignition, this means that the fuel they burn is a vapour ignited under pressure from an electrical spark using spark plugs.Diesel engines are known as Compression Ignition, this means the fuel they burn is diesel fuel, the process is that the engine has a higher compression ratio to heat up the cylinder combustion chamber, which then has diesel fuel injected into the compressed air under high pressure which then self ignites, in other words it explodes, or it may implode, then nitrogen expands to expand the volume of the cylinder. Depending which is right, explode or implode, I would need to look at some Thermodynamics to refresh myself and then give further clarification.But in the main the above is correct