Adsorption Theory explains how molecules from a gas or liquid adhere to a solid surface. This process occurs when the attractive forces between the surface and the molecules are stronger than the forces between the molecules themselves. The result is a concentration of molecules at the surface, forming a thin layer. The theory is crucial in various fields, including catalysis, water treatment, and separation processes. It helps scientists understand how materials like activated carbon can effectively remove pollutants from water or how catalysts enhance chemical reactions by providing a surface for reactants to adhere to.