Definition
Osmosis is the net diffusion of water molecules from a dilute solution to a concentrated solution when the two are separated by means of a semi-permeable membrane.

Basic Explanation
When the two solvents having different osmotic concentrations are separated by the means of a semi-permeable membrane, they move from a region of higher chemical potential to a region of lower chemical potential. This movement of the solvent particles (water) is called Osmosis.
Basically, this involves the diffusion of solvent across a semipermeable membrane in a biological system.
Pure water has maximum free energy, diffusion dissolves into it, and the free energy of its water molecule decreases.
Cellular osmosis
Cellular osmosis is the mechanism through which cells help in regulating their environmental conditions, known as osmotic pressure. It involves the movement of solvent molecules across the cell membranes. It helps maintain a balance between two solutions with different concentrations.
Factors influencing osmosis
1. Concentration
The rate of osmosis reaction depends on the difference between the two solution concentrations. The higher the solute concentration, the lower will be the diffusion ratio of absorbing water through osmosis. At higher temperatures, the diffusion rate becomes higher.

2. Temperature
Higher temperatures result due to higher concentrations and osmosis becomes faster at increasing temperatures.

3. Pressure
Pressure can decrease or increase the process of osmosis.
When pressure is applied to higher solute concentration it reduces the flow of solvent.
When pressure is applied to lower solute concentration it increases the flow of solvent.