Adsorption is a surface phenomenon where molecules of a gas or liquid (adsorbate) accumulate on the surface of a solid or liquid (adsorbent), creating a film of the adsorbate. This process differs from absorption, where substances are taken up volumetrically. Adsorption occurs due to the attractive forces between the adsorbate and adsorbent surfaces, often driven by the aim to minimize the surface energy. It is widely utilized in various applications including water purification, in air filters, and in catalysis, where specific materials adsorb contaminants or reactants. The efficiency of adsorption depends on the nature of both the adsorbate and adsorbent, temperature, and pressure of the system.