Diffusion - It is defined as the movement of particles from higher concentration to the lower concentration resulting in Lowering of pressure Gradient.
Effusion - Effusion is when there is a barrier with one or many small holes that prevent the gas to expand into the new volume unless a gas molecule happens to travel through the hole
Osmosis - Osmosis is basically the same thing as diffusion but it deals solely with water.Passage of a solvent (such as water) from a lower-concentration solution to a higher-concentration solution, through a semi-permeable membrane (that allows the solvent to pass but not what is dissolved in it) separating the two solutions