If I have a glass of water, and the vapor pressure is the point of equilibrium where the liquid molecules are becoming gases and the gas molecules are colliding and becoming liquid at the same rate, does that mean none of the liquid is lost? I feel as if I am misunderstanding this concept because when I leave my cup of water on the table and come back to it later on I usually notice that there's less water in the cup because it evaporated.
Yes, the vapor pressure is the point of equilibrium between the liquid and the vapor. But air moves about so the liquid never saturates the air and an equilibrium is never reached. So more and more water evaporates until it is all gone.