Osmosis is the diffusion (or scattering) of water molecules through a semi-permeable membrane of a region of high concentration for a region of low concentration, until a state of dynamic balance is reached.
Osmosis is the movement of water molecules through a partially permeable membrane to a gradient of water potential. More specifically, it is the movement of the water through a permeable membrane partially of an area of high water potential (low concentration of solute) for an area of low haricot potential (high concentration of solute). It is a physical process where if it dislocates the vehicle, without energy entrance, through a semi-permeable membrane (permeable to the solvent, but not it solute) that it separates two solutions of different concentrations. Osmosis liberates energy and can be made to make the work. The osmosis is a passive process, as the diffusion.
Liquid movement of the solvent is from intent the least (hypotonic) for the most concentrated (hypertonic), solution that tends to reduce the difference in the concentrations. This effect can be fought by the increase of the pressure of the hypertonic solution, with regard to the hypotonic. The osmotic pressure is defined as being the pressure necessary to keep a balance, with no liquid movement of the solvent. The osmotic pressure is a linking property, what it means that the osmotic pressure depends on the molar concentration of solute, but not on its identity.
The osmosis is important in the biological systems, as many biological membranes are semi-permeable.