Assuming you are serious. Go to top right of yahoo answers screen and type 2 words: gasoline fraction Click on www.petrostategies.org ..
Basically, they take crude oil from the ground, and heat it to different temperatures, to get different types of liquid, like gasoline, kerosine, naptha etc.
Cars need it to make the engine run. Gasoline explodes inside the motor, and releases heat and pressure. The pressure makes the pistons go up and down, which turns the crankshaft, which makes the car move.