Desorption is the process by which a substance is released from or through a surface. It occurs when molecules that were previously adsorbed, or attached, to a surface break free and enter the surrounding environment. This process is important in various fields, including chemistry, environmental science, and materials science. In practical applications, desorption is crucial for processes like catalysis, where reactants must be released from a catalyst's surface to allow for new reactions. It also plays a role in gas sensors, where the detection of gases relies on the desorption of molecules from sensor surfaces to trigger a response.