The term for the transport of substances across a cell membrane is called membrane transport. This process can be categorized into two main types: passive transport, which does not require energy and occurs along concentration gradients, and active transport, which requires energy to move substances against their concentration gradients. Mechanisms involved in membrane transport include diffusion, facilitated diffusion, and endocytosis. Understanding how substances move across cell membranes is essential for grasping various physiological processes in living organisms.