In reference to diffusion passive really means?

In the context of diffusion, "passive" refers to the movement of molecules across a membrane without the input of energy. This process relies on the concentration gradient, where substances move from areas of higher concentration to areas of lower concentration until equilibrium is reached. Passive diffusion is a fundamental mechanism that allows cells to obtain nutrients and expel waste efficiently. Unlike active transport, which requires energy to move substances against their gradient, passive diffusion occurs naturally and spontaneously.