The hydrogen bond in polar molecules occurs only in compounds that have hydrogen bonded to N, O, or F.
These very highly electronegative elements create a partial positive charge on the hydrogen.
The H atom is attracted to the partial negative charge on an N, O, or F atom in another molecule.
The hydrogen bond is an attraction but not a true chemical bond such as ionic or covalent bonds. It is much weaker.
However, the hydrogen bond is a strong intermolecular bond.