Chromatography is a separation technique, used to separate many different liquids from a substance, for example the pigments in ink. As the water moves up the paper, the ink dissolves into it. The less soluble liquids or pigments are depostited lower down than the more soluble liquids.
Locating agents are used to locate colourless compounds which have been separated in the chromatography. Locating agents are applied to the chromatogram to make these visible.