Hydrogen bond can be defined as an attractive force which binds hydrogen atom of one molecule with the electronegative atom (F, O or N) of another molecule. Following conditions should be fulfilled by a molecule for the formation of hydrogen bond.
(a) Hydrogen atom should be linked to a highly electronegative atom, such as F, O or N through a covalent bond.
(b) The size of the electronegative atom bonded covalently to the hydrogen atom should be small.
Types of H-bonding :
Intermolecular hydrogen bond:
When hydrogen bond is formed between the hydrogen atom of one molecule and the electronegative atom of another molecule of the same compound (such as HF) or different compounds (such as water and alcohol), it is known as intermolecular hydrogen bond.

Intramolecular hydrogen bond :
When hydrogen bond is formed between the hydrogen atom and an electronegative atom, present in the same molecule, it is known as intramolecular hydrogen bond.
H-bonding is stronger than van der Waals forces.