Are you sure they didn't say intermolecular forces? Condensation is a physical process-- there should be no change in an individual molecule. However, as you decrease the temperature when something is boiling, you lower the average kinetic energy of those boiling gaseous molecules. As they move slower, intermolecular forces may start making bunches of gaseous molecules 'stick' together and clump. Eventually you'll get condensation.
If we take water as an example: in the gas phase they have really high kinetic energy and the hydrogen bonds aren't strong enough to keep them stuck together, so they're just flying around generally independently. As you lower the temperature, hydrogen bonding starts helping them stick together into droplets and you'll eventually get a liquid.