Diesel and petrol are the two main engines we have today, and the diesel engine is an inner combustion engine that uses diesel as fuel. Diesel engines are quite effective, and the combustion procedure of the diesel engine utilizes a distinct technology.
It takes air, which is compressed to 200 bars, and fuel is introduced into the air at the expansion stroke. With the high pressure and temperature, an auto-ignition takes place. On the other hand, the diesel engine does not need a spark plug, and as a matter of fact, it isn't easy to start a diesel engine.
A petrol engine is an inside combustion engine that uses petrol as fuel. This engine uses a different method of mixing fuels and air. Unlike diesel, it uses a spark plug, and the fuel and air are pre-mixed before the compression process.