That means benzene has 3 double bond right ?

Benzene (C₆H₆) is an aromatic hydrocarbon. Its structure is a six-membered ring of carbon atoms. While its molecular formula suggests it could have alternating single and double bonds, experimental evidence shows that all carbon-carbon bonds in benzene are identical in length and strength, intermediate between a single and a double bond.

This is explained by resonance. The six π electrons in benzene are not localized between specific pairs of carbon atoms but are delocalized over the entire ring. This delocalization creates a stable, continuous cloud of electrons above and below the plane of the ring.

So, instead of 3 distinct double bonds, benzene is often represented with a circle inside the hexagon to indicate this electron delocalization and aromatic stability.