During the fractional distillation of crude oil:
Some hydrocarbons have low boiling points. They do not condense but leave the column as gases. Some hydrocarbons have high boiling points. They leave the column as hot liquid bitumen.
The different, useful mixtures separated from crude oil are called fractions. This is because they are only part of the original crude oil.
These fuels are non-renewable - they are being used up faster than they are being formed. This means that they will run out one day if we carry on using them.
One way to remember the names of the fractions is 'Good Penguins Keep Diving For Bass'.