If your cold glass of lemonade seems to be sweating in the heat, it's just the condensation, the little drops of water that form in the humid air. Condensation happens when a gas turns into a liquid.
That lemonade feels wet in your hand because of the condensation on the glass. As the heated air reaches the cold water, the surface of that water begins to evaporate, but it turns back to liquid. Clouds are caused by condensation as well. Condensation can also describe the act of making something shorter, like the condensation of an unabridged dictionary to one that is geared to elementary school students.