Latent heat is the energy given off or absorbed during a change of phase. Whenever a substance changes form a gas to a liquid or from a liguid to a solid this latent heat is given off. Whenever a substance changes from a solid to a liquid or from a liquid to a gas this latent heat is absorbed from the surroundings. While a substance is changing phase, no temperature change takes place. So as heat energy is added to or removed from a substance, this heat energy is going either to sensible heat (temperature change) or to latent heat (phase change), but not both at once.

Your body uses latent heat during the summer as it sweats. As the persperation evaporates, the vapor absorbs this latent heat of vaporization from your body, cooling it.

The latent heat of steam (water in the gaseous phase) is very high. This makes steam an ideal subsatnce to transfer large amounts of energy, both the latent heat as a gas, and as sensible heat due to its high temperature.