Latent heat is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process, usually a first-order phase transition. Simply put, latent heat is the heat required for an object to change phase (melt, boil, freeze, etc.).
Examples of latent heat:
When water is boiled and the temperature remains at 100°C until the last drop evaporates, because of the latent heat of vaporization, the added heat in the water is absorbed and carried away by releasing vapour molecules.
In thermodynamics, the triple point of a substance is the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium. It is that temperature and pressure at which the sublimation curve, fusion curve and the vaporisation curve meet.