Osmosis: it is the passive movement of water through the cell membrane from an environment with lesser concentration of a solute (e.g. salt) to one with greater concentration, until the equilibrium is reached (i.e. the concentration is equal on both sides of the membrane).
Simple diffusion: Not only water can move through the cell membrane, some small molecules, such as glucose, can do it too. In this case, the solute will move from the enviorement with greater concentration to the one with lesser concentration, until the equilibrium is reached.
Facilitated diffusion: Some others molecules can diffuse through the cell membrane using channel proteins or carrier proteins.
Active transp