The Valence Bond (VB) model describes the bonding in covalent compounds as:

Single bonds. 2 centers-2 electrons.

Double bonds. 2 centers-4 electrons.

Triple bonds. 2 centers-6 electrons.

The resonance concept can be considered as a limitation of VB model to explain certain bond situations. The resonant structures can be considered as extreme situations of the real case. The resonant structures do not correspond to any real compound, are not real. The real structure is not the result of an equilibrium between the resonant structures since such structures are not real.