Chromatographic methods are classified based on various factors.

The first classification is based on the physical states of the mobile and stationary phases.

For example, in gas-liquid chromatography, the mobile phase is a gas, while the stationary phase is a thin liquid coating.

In cases like 'gas chromatography', where only one phase is mentioned, the given phase is the mobile one.  

The second classification is based on the equipment supporting the stationary phase, which includes column and planar chromatography.

In column chromatography, the stationary phase is either packed into a column or coated inside a narrow tube, and the mobile phase passes through under gravity or pressure.

In planar chromatography, the stationary phase is immobilized on a flat planar surface, and the mobile phase travels by capillary action.

The third classification is based on the chemical or physical mechanism for separation.

These include adsorption, partition, ion exchange, and size-exclusion chromatography.