DIMENSION

In the world of Dragon Ball, there are Universes, Alternate Timelines and DIMENSIONS.

Universes were introduced in Dragon Ball Super, there are 12 Universes where 6 of them are similar to the other six of them (having similar people, similar planets). The Dragon Ball Series is in Universe 7.

An Alternate Timeline is a copy of a Universe which was created because a timetraveller went to the past and altered something, this alternate timeline can easily be created, even stepping on a simple plant could change the future. But that future from then is an alternate version from the Timeline of the traveller. This was shown in the series of Future Trunks, who went to the past to prevent something, but instead created an Alternate Timeline, which means that when he came back to his Timeline, nothing had been changed, but the past he went to, had a completely different future from then.

DIMENSIONS are different Futures that havent been created by Travellers, an example is Dragon Ball GT and Dragon Ball Super, they are both a sequel to Dragon Ball Z, but are different Universes, this has been created by the writer of the series.

Eventually, the Dragon Ball AF Universe and the Dragon Ball Super Future comes together after the great merger