Food producers use distillation as a way to purify water by boiling it, then collecting the steam and cooling it so it condenses into a purified product. Oil refineries use fractional distillation to separate petroleum into various components with different boiling points.
One method of distilling water at home involves heating water in a pot with a smaller container inside the pot. An inverted lid on the larger pot provides a collection point for the vapor that forms when the water is heated. Putting ice on the lid cools the steam and converts it back into a liquid. As the water liquefies, it moves to the center of the lid and drips into the smaller container.
Fractional distillation of petroleum uses the variations in boiling points of the components of crude oil to separate them. The refiner heats crude oil, and the vapors pass through a condensing tower. The boiling point of each compound determines how high it travels up the tower before condensing and collecting on a tray along with compounds that have a similar boiling point. Each tray drains to a separate collection container.
Petroleum refiners use both atmospheric and vacuum distillation. Vacuum distillation is particularly useful for further refining the remains of crude oil after distilling at atmospheric pressure. The vacuum lowers the boiling point of the compounds, so the refiner is able to separate them without introducing so much heat that they undergo chemical reactions.