liquids are led out of the column at different heights
Small hydrocarbon molecules have weak intermolecular forces, so they have low boiling points. They do not condense, but leave the column as gases. Long hydrocarbon molecules have stronger intermolecular forces, so they have high boiling points. They leave the column as hot liquid bitumen.
Crude oil fractions
The different, useful mixtures are called fractions. This is because they are only part of the original crude oil.
One way to remember the names of the fractions is: Lazy Penguins Keep Drinking Hot Beer.