Petrol, kerosene and diesel oil are fuels that we get from crude oil, which is separated into fractions by fractional distillation. Petrol is used in cars, kerosene in aircraft and diesel oil in some cars and trains. Methane is the main gas in natural gas, which is found underground, often near crude oil.
Crude oil and natural gas are fossil fuels. They formed over millions of years from the remains of tiny sea creatures that were buried under mud and squeezed and heated.
They are non-renewable. They take millions of years to form, so they are being used up much faster than new supplies are made, and one day they will run out.