Latent Heat, Vapor pressure and Equilibrium
All is about  3 basic principles. 


Liquid evaporation consumes thermal energy, taken from liquid itself or surrounding. Vapour condensation releases this energy.
Liquid saturated vapour pressure (about) exponentially raises with temperature.
If saturated vapour pressure exceeds external pressure, liquid boils. If vapour pressure exceeds the saturated vapour pressure, vapour condensates.