Fractional Distillation is the breaking up of crude oil into its various fractions (Hydrocarbons)

The smaller the hydrocarbon, the more volatile and the less viscous it becomes. The column allows each fraction to evaporate at different points,

The first fraction - Refinery Gases- is used in gas for stoves amongst other things.

The next fraction is gasoline (Petrol). This is used for fuels in cars, and has a very high demand.