In such a process, a mixture is separated into fractions, which have compositions that vary according to a gradient.
A fraction can be defined as a group of chemicals that have similar boiling points.
[1] It is used to produce liquor and various hydrocarbon fuels, such as gasoline, kerosene and diesel.
A fraction is the product of a fractionating column, a vast chamber designed to separate different substances (such as crude oil) based on their boiling point.
For a simpler definition a fraction is a part of the fractionating column where a compound with one boiling point can be separated from other compounds with different boiling points.