Benzene is the hybrid of the resonating structures shown below:-

Now, all the six carbon atoms in benzene are sp₂ hybridized. The two sp₂ hybrid orbitals of each carbon atom overlap effectively with the sp₂ hybrid orbitals of adjacent carbon atoms to form six sigma bonds in the hexagonal plane. The remaining sp₂ hybrid orbital on each carbon atom overlaps with the s-orbital of hydrogen to form six sigma C–H bonds. The remaining unhybridized p-orbital of carbon atoms has the possibility of forming three π bonds by the lateral overlap of –

The six π orbitals and their electrons are delocalized and hence can move freely about the six carbon nuclei. Even after the presence of the three double bonds, these delocalized π-electrons stabilize benzene.