Whis explaining the nature of the universes to Goku and Vegeta
The Dragon Ball universes, or the Dragon Ball world, are the chain of universes within the Dragon Ball series.
There are twelve in total, but the only known universes as of yet are the sixth and seventh universe. Any of the universes combined that add up to thirteen is a twin universe (i.e. the first and twelfth universes, second and eleventh universes, third and tenth universes, fourth and ninth universes, fifth and eighth universes, and the sixth and seventh universes).
All events that occur in Dragon Ball, Dragon Ball Z, and Dragon Ball GT, as well as the Battle of Gods Saga and the Resurrection ‘F’ Saga in Dragon Ball Super take place in the seventh universe. The sixth universe is set to appear in the Champa Saga in Dragon Ball Super.