Osmosis is the movement of water particles from an area of high concentration of water particles to an area of low concentration of water particles across a semi permeable membrane
Diffusion is the movement of particles from an area of high concentration of particles to an area of low concentration of particles across a partially permeable membrane
Plasmolysis is the shrinking of the cytoplasm if a plant cell in response to diffusion of water out of the cell and into a high salt concentration solution as the cell membrane would pull away from the cell wall
Hope this helped