Dipole-dipole interactions are attractive forces that occur between polar molecules, which have a positive end and a negative end due to uneven distribution of electrons. These interactions arise because the positive end of one molecule is attracted to the negative end of another, leading to a stable arrangement. These forces 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 interactions, influencing properties like boiling points and solubility in polar solvents.