Passive transport is the movement of substances across the cell membrane without the use of energy.
Active transport requires energy from ATP to move substances against their concentration gradients, while passive transport does not require energy as it moves substances with or down their concentration gradients.
The concentration gradient is the difference between the concentrations of molecules on either side of the membrane.
Osmosis is the diffusion of water through a selectively permeable membrane, with water moving from an area of lower solute concentration to higher solute concentration.
Diffusion is the passive movement of molecules from an area of high concentration to low concentration until equilibrium is reached.
Facilitated diffusion involves carrier proteins that bind to specific molecules and facilitate their passage through the plasma membrane.