Colligative properties are properties in chemistry that can only be applied to solutions. These properties depend on the ratio of the solute to the solvent in the solution and get numerically larger or smaller if the ratio changes.
Colligative properties depend on the number of particles found in the solute and on the solvent in a solution. Unlike other chemical properties, colligative properties do not depend on the identity of the solute or of the solvent. Few properties of a solution can be termed as colligative properties, but the vapor pressure depression, boiling point elevation, freezing point depression and osmotic pressure are all examples of colligative properties.
The vapor pressure depression is defined as the change in vapor pressure of a solvent that occurs when a new solute is added to said solvent. This property depends on the mole fraction of the solute and not the solvent. Boiling point elevation and freezing point depression both refer to the concept that states when you add solutes to a liquid solvent, its boiling point will immediately elevate and its freezing point will lower to account for the addition of the solute. Osmotic pressure is the pressure that solutes expend on molecules in the solvent. When new solutes are added to a solvent, the osmotic pressure changes.