What do intermolecular forces have to do with polar and/or non-polar molecules?

There are three main types of intermolecular forces. London Dispersion, dipole-dipole, hydrogen bonding. All molecules exhibit London dispersion forces. Polar molecules exhibit both LDF and dipole-dipole because of the differences on electronegativity. If hydrogen is bonded with one of the very electronegative molecules (N,O,or F), it has hydrogen bonding and is usually polar (Ex. Water).