The energy required to change the phase of a substance is known as a latent heat. Latent means hidden. When the phase change is from solid to liquid it is termed as the latent heat of fusion, and when the phase change is from liquid to a gas, it is known as the latent heat of vaporisation.
When we boil water to evaporate 100 °C, all the given heat is absorbed by the liquid. This absorbed heat is called latent heat of vaporization.