Dipole-dipole interactions are attractive forces that occur between polar molecules. These interactions arise because polar molecules have regions of partial positive and negative charges, leading to an uneven distribution of electron density. When two polar molecules come close together, the positive end of one molecule is attracted to the negative end of another, creating a stable interaction. These interactions are generally stronger than London dispersion forces but weaker than hydrogen bonds. The strength of dipole-dipole interactions depends on the polarity of the molecules involved; more polar molecules exhibit stronger dipole-dipole interactions, influencing properties like boiling and melting points.