Fractional distillation is needed where there are many different liquids mixed together, all with different boiling points. Fractional distillation is used to extract each of these substances from each other. Each of these separated components are called fractions. A tall column is fitted above the mixture, with several condensers coming off at different heights.
The column is hot at the bottom and cool at the top. The mixture evaporates at the bottom of the column and the rises through the column as a gas. The substances or “fractions” with highest boiling points condense at the bottom and substances or “fractions” with lowest boiling points condense at the top.
Each condenser can have a different temperature allowing you to capture materials as they rise. The condensers temperature would decrease as you move up the column. The most common use of fractional distillation, and most importantly, is separating crude oil into it’s useful components.