My textbook says:
Dipole-dipole forces are 1% as effective as covalent bonds and the strength of a hydrogen bond is generally twenty times less than that of a covalent bond.
What do these statements mean?
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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.
