Resonance stabilization is the energy of a real molecule compared with its anticipated energy for the best resonance structure that may be drawn for the said molecule. The anticipated energy is based on the types and amount of bonds present in the resonance structure.
Molecules are considered stabilized when there are multiple valid resonance structures available for a particular molecule. The resonance stabilization is greater if there are more nearly equivalent number of resonance structures in energy. Molecules that only retain one valid resonance structure, such as methane, are not considered stabilized. Finally, the stabilization is maximized when resonance structures are exactly equal.