Thin layer chromatography (TLC) is a technique used to separate non-volatile mixtures on a sheet coated with an adsorbent material like silica gel. TLC functions on the principle that compounds have different affinities for mobile and stationary phases, affecting their migration speed. To perform TLC, a sample is applied to the plate and developed in a solvent, which carries compounds up the plate at different rates. The plate is then visualized to view separated components, and Rf values are calculated to help identify compounds based on their distance traveled up the plate relative to the solvent front.