Which process results in the formation of water drops on the outer surface of a glass filled with ice?

Condensation is the change of the physical state of matter from gaseous phase into liquid phase. The temperature of the ice cold water is close to zero. The air around the container consists of water vapour, which accounts to humidity. When the water vapour comes in contact with the outer surface of glass containing ice cold water, there is a change in physical state of water vapour to water in liquid phase due to lower temperature and condensation. Hence,  it accounts for the water droplets on the outer surface of a tumbler or a glass containing ice cold water.