What is H - bonding

A hydrogen bond is a the electrostatic attraction between two polar groups that occurs when a hydrogen (H) atom covalently bound to a highly electronegative atom such as nitrogen (N), oxygen (O), or fluorine (F) experiences the electrostatic field of another highly electronegative atom nearby.

In simple words, consider the molecule H⁺-F^-; here H will have a partial positive charge and F will be with partial negative charge. Now if another H-F molecule comes in their proximity then a H-bond will be formed. Please remember: H-bond is just an electrostatic attarction, there is no sharing of electrons here.

H⁺-F^- ------ H⁺-F^- ----- H⁺-F^- {------ are H bonds}

H-bonds have a huge importance in modern day chemistry; as the organic molecules such as NH₃, sugar are soluble in water because they have the ability to form H-bonds with water molecules.