Osmosis is the movement of water from an area of low concentration of solute to an area of higher concentration of solute. A solute is atoms, ions, or molecules dissolved in a liquid. The rate of osmosis is determined by the total number of particles dissolved in the solution. The more particles dissolved, the faster the rate of osmosis.
If a membrane is present, water will flow to the area with the highest concentration of solute. Osmotic pressure is the pressure created by water moving across a membrane due to osmosis. The more water moving across the membrane, the higher the osmotic pressure.