What is latent heat and how is it important in the atmosphere?
The energy absorbed by water in order for it to change state.
When liquid water changes state to water vapor due to heating, that heat is held in the molecules themselves when they are in the gaseous state. That is latent heat. When the molecules return to a liquid state the latent heat is released as sensible heat (heat you can feel basically).
It is important in the atmosphere because it is the primary factor involved in the formation of convective clouds and the stability/instability of the atmosphere.
Without getting into too great an explanation, latent heat is released as sensible heat during cloud formation. This means that the air involved will likely be warmer than the air surrounding it. Warm air rises, and rising air is unstable.