Molecules are characterized by inter and intra molecular forces of interaction. intramolecular forces are those forces that are present within the molecular framework. Ionic and covalent are typical examples of intra-molecular forces of interaction which held atoms together and assist in formation of molecules. On other hand, intermolecular forces of interaction, occurs between two different molecules. They are further sub-categories as dipole-dipole, dipole-induced dipole, van der Waal's, hydrogen bonding etc.
In current context, hydrogen bonding exist if hydrogen atom in a molecule is attached to electronegative elements like O, F or N. Classic example of the system exhibiting hydrogen bonding is pure water. In pure water, water molecules are held together by hydrogen bonding.