Chromatography is the separation of a mixture by passing it in solution or suspension or as a vapor through a medium in which, the components move at different rates.
It involves a sample being dissolved in a mobile phase (which may be a gas, a liquid or a supercritical fluid).
Then, mobile phase is then forced through an immobile, immiscible stationary phase.
The phases are chosen such that components of the sample have differing solubilities in each phase.