The hydrogen bond can be defined as the attractive force which binds hydrogen atom of one molecule with the electronegative atom (F, O or N) of another molecule. The hydrogen bond is usually represented as X - H........Y where X and Y are highly electronegative atoms such as F, O and N. Note that the description of “donor” and “acceptor” in hydrogen bond refers to the proton, in the hydrogen bond X - H........Y, the X - H group act as hydrogen donor to acceptor atom Y. In contrast, in a coordination bond the donor atom is the one that bears the electron pair.
The strongest hydrogen bond resemble covalent bonds, the weakest one are like van der waals interactions and the majority have energies lying between these two extremes. 
Some non-conventional hydrogen bonds that do not conform the definition above are also known. Hydrogen bond is universal and appear in several compounds.