Hydrogen bond is a bond, which forms dipole-dipole attraction when hydrogen atom that is covalently bond to a highly electronegative element experiences electrostatic force of attraction due to another highly electronegative element.
The hydrogen bond donor is the atom, to which the hydrogen atom is bonded by a covalent bond. It is a highly electronegative element, such as, fluorine, nitrogen or oxygen. The hydrogen bond acceptor is the atom, which has a lone pair of electrons and is a highly electronegative element helping in the formation of a hydrogen bond.