Strength of Dipoles, Covalent bonds and H-Bonds
It means that of the three forces, dipole-dipole forces are the weakest, hydrogen bonding is the second weakest, and covalent bonds are the strongest. Now, dipole-dipole attraction happens between an ion and a polar molecule. Due to a net dipole movement, this is weak. In comparison to a covalent bond, it has only $\frac{1}{100}$ the efficacy. A hydrogen bond is a force between H and either N, O, or F, the three most electronegative elements. These are classified as d-d forces, but due to the differing electronegativities, they are a tad stronger. Covalent bonds are much stronger than either, $20$ times more than the H-bond and $2000$ times stronger than the d-d force. A covalent bond involves the sharing of electron pairs between atoms, generally two non-metals. There are also ionic bonds and metallic bonds, an ionic bond involving the transfer of electrons, such as $\ce{NaCl}$ and a metallic bond being between metals.