The vaporization process that occurs on and below the surface of a liquid is evaporation. Evaporation describes the conversion of a liquid to a gas, while condensation refers to the conversion of a gas to a liquid.
Evaporation results from increased temperature or lowered pressure. Condensation happens when the temperature is lowered or the pressure is increased. Infusing a liquid with energy moves the atoms or molecules around faster, and the ones on the surface escape to the atmosphere. The heat gives them enough energy to break the Van der Waals and other cohesion forces that sustain a liquid. This heat of vaporization must be removed from a gas to turn it back into a liquid.