In organic chemistry, hydrocarbons can be divided into aromatic compounds which contain aromatic rings, also known as benzene rings, and aliphatic compounds which do not.
Examples:
Methane is an aliphatic compound, and contains no aromatic rings.
Benzene is an aromatic compound, as it is an aromatic ring.
Toluene is an aromatic compound, as it contains an aromatic ring bonded to a methyl group.