It is the phenomenon in two or more Lewis structures can be written for the compound.
When two or more Lewis structures can be written, these structures are called resonance contributing structures or canonical structure.
The actual structure of a compound is the hybrid of all these resonance contributing structures.
Resonance hybrid resemble all the structures up to some extent but not identicle to any one of them.
Real structure of benzene is a hybrid of wo kekule’s and three Dewar structures.
Kekule structure contribute greater as compared to Dewar structures.(kekule : 78%, dewar : 22%)
So the real molecule may resemble one structure more than the other one, since the hybridhas lower energy than any of the contributing structure.What is Resonance in benzene? - Quora