Vapor pressure can be defined as the pressure of gas at it's equilibrium between vaporization and condensation. Therefore the air will only store so much water in it's vapor form which causes the humidity and if cooled or heated it is either evaporated further or released as precipitation.
The term "dew point" refers to when air is at a specific pressure where the water vapor and the liquid water in the air is at equilibrium where the water is condensing at the same rate it is evaporating.
Question from the Professor:
If you hang clothes out to dry when the temperature is 20 C and the dew point is 20 C will they ever dry?