Langmuir adsorption theory describes how molecules adhere to a solid surface. It assumes that adsorption occurs at specific sites on the surface, where each site can hold only one molecule. This leads to a saturation point, where no additional molecules can be adsorbed, resulting in a maximum coverage of the surface. The theory also introduces the concept of a dynamic equilibrium between the adsorbed molecules and those in the surrounding environment. This means that while some molecules are sticking to the surface, others are detaching, allowing for a balance that can be influenced by factors like temperature and pressure.