Adsorption is a process where molecules from a gas or liquid adhere to the surface of a solid or liquid. This occurs due to attractive forces between the adsorbate (the substance being adsorbed) and the adsorbent (the material that captures the molecules). Unlike absorption, where a substance is taken up into the bulk of another, adsorption only involves surface interactions. This phenomenon is important in various applications, including water purification, where contaminants are removed from water using materials like activated carbon. It also plays a crucial role in industrial processes, such as catalysis, where reactions occur on the surface of catalysts like platinum or nickel.