Benzene is an aromatic hydrocarbon. Instead of having three short double bonds and three long single bonds (above, left), it has six medium-length bonds (above, right).
A double bond is really two bonds, with two electrons in each bond, so four electrons in total in a double bond. Two electrons from each double bond in benzene (if the double bonds really existed, which they don't) are smeared over all six carbon atoms.
Whenever electrons are not confined to a bond between just two atoms, they are called declocalised electrons.
Developing Fuels is the second unit in the Salters Advanced Chemistry course.