The point at which the vapor pressures of a substance in its gas, liquid, and solid forms are all in equilibrium is called the triple point.

Here's a breakdown:

* Vapor Pressure: This is the pressure exerted by the vapor of a substance when it is in equilibrium with its liquid or solid phase.

* Equilibrium: This means that the rates of evaporation and condensation (or sublimation and deposition in the case of solids) are equal.

* Triple Point: This is a specific temperature and pressure at which all three phases (solid, liquid, and gas) of a substance can coexist in equilibrium.

Think of it this way:

Imagine a closed container with a substance inside. At the triple point:

* Some of the substance will be in the solid state.

* Some will be in the liquid state.

* Some will be in the gaseous state.

The vapor pressure of the gas will be equal to the vapor pressure of the liquid, and both will be equal to the vapor pressure of the solid. This creates a delicate balance where all three phases can coexist.

Important Note: The triple point is a unique and fixed point for each substance, unlike the melting point or boiling point which can vary slightly with pressure.