Definition: Van der Waals Forces are the weak forces which contribute to intermolecular bonding between molecules. Molecules inherently possess energy and their electrons are always in motion, so transient concentrations of electrons in one region or another lead electrically positive regions of a molecule to be attracted to the electrons of another molecule. Similarly, negatively-charged regions of one molecule are repulsed by negatively-charged regions of another molecule.
Van der Waals forces are the sum of the attractive and repulsive electrical forces between atoms and molecules. These forces differ from chemical bonding because they result from fluctuations in charge density of particles.
Examples:hydrogen bonding, dispersion forces, dipole-dipole interactions