Diffusion is the process by which particles or molecules spread or move from an area of higher concentration to an area of lower concentration. It is a fundamental process in various fields such as physics, chemistry, biology, and engineering. Diffusion can occur through various mediums such as gases, liquids, and solids, and is influenced by factors such as temperature, pressure, and the properties of the substance being diffused. Researchers study diffusion to understand how substances move and spread in different environments, as well as to develop models and theories to predict and control diffusion processes.