* Osmosis is the movement of water across a semi-permeable membrane from an area of high water concentration to an area of low water concentration. This movement is driven by the difference in water potential, not by a specific protein.

* Facilitated diffusion is the passive movement of molecules across a membrane with the help of a transport protein. This movement still goes down the concentration gradient, but it is facilitated by the protein.

Aquaporins are integral membrane proteins that act as channels for water molecules. They allow water to move across the membrane much faster than it could on its own. However, they do not actively transport water against the concentration gradient; they simply facilitate its movement down the gradient.

Therefore, while aquaporins are essential for the rapid movement of water across membranes, they are not involved in osmosis per se. They are involved in facilitated diffusion of water.