The transport equation is a mathematical equation used in fluid dynamics and other scientific fields to study the transport of quantities such as mass, momentum, and energy. It describes how a quantity is transported through a medium by advection (the movement of the medium itself) and diffusion (the random motion of particles within the medium). The transport equation is often used in the study of phenomena such as heat conduction, fluid flow, and atmospheric dynamics. It provides a framework for understanding how quantities move and change in a physical system over time.