Intermolecular forces describes the force that acts between molecules. This is in contrast to intramolecular forces, which act on atoms within molecules to hold it together.
There are three main types of intermolecular forces:
Collectively, London forces and dipole-dipole forces are referred to as van der Waal’s forces. In terms of intermolecular attractive strength (and boiling point), LDF < dipole-dipole < hydrogen bonding.