What roles do the mobile phase and stationary phase play in chromatography?

In chromatography, the separation of a mixture relies on the interaction between two distinct phases: the stationary phase and the mobile phase.1

The Stationary Phase

The stationary phase is a fixed material—typically a porous solid or a thin film of liquid—over which the mobile phase passes. It acts as the medium that interacts with the components of the sample. Because different substances in a mixture possess varying degrees of affinity for this phase, they are retained for different lengths of time as they travel through the system. Components with a stronger attraction to the stationary phase move more slowly, while those with a weaker attraction are flushed through more rapidly.1

The Mobile Phase

The mobile phase is the fluid (either a liquid or a gas) that flows through or over the stationary phase. Its primary role is to transport the sample through the chromatographic system. As it carries the mixture, the mobile phase facilitates the partitioning of components between itself and the stationary phase, ultimately enabling the separation of the mixture's constituents based on their relative affinities for the two phases.1