What is the difference between osmosis and diffusion?

Osmosis is the net movement of water from a region of high water potential to a region of low water potential through a partially permeable membrane.meaning if one place has a high water to substrate ratio let say 4:1 and if the other side of the membrane has a ratio like 5:10 (water:substrate) water from the region of 4:1 will move to the region of 5:10 ( doesn't have to have a lower amount of water rather a lower ratio of water to substrate. )