An Instantaneous-dipole-induced-dipole bond (or Wan der Waal forces) are attractions between two unpolarized molecules. Their are three stages involved in this kind of attraction. First a dipole instaneously happens (1), then this dipole is induced to the second molecule (2). Once both molecules have dipoles, they are attracted to each other (3).
This type of attraction is involved in polymer chains and determines how dense and strong they are.