The multiverse is an infinite or finite set of universes parallel to each other. In Dragon Ball there are two multiverses, the DBS 12(Formerly 18) universes which are all contained in a single timeline, and the Xenoverse and Heroes multiverses which are infinite and are contained in the Chasm of Time. In the Xenoverse and Heroes multiverses the timelines are represented as crystals and are called Time Chasm Crystals.
The universes are 3rd/4th dimensional sealed spheres that contain: planets, stars, nebulae(solar systems), galaxies, and various pocket dimensions. The universes were created by Tori-Bot, or in-universe, by the Kaioshin and Tokitoki, the universes are all kept in an outside dimension on a giant jelly fish near Zeno's palace floating on top of rock pillars.
 Xenoverse proved all universes are in a single timeline.
 Heaven, Hell, Makai, The Living Universe, Room of Spirit and Time, Sugoroku Space, Kaioshin Realm, Emma Realm, Dai Kaio's Planet.
 The Dead Zone.
 Dai Kaio's Extradimensional Space.
 Omega's/Demigra's void dimension
 Time Breaker Pocket dimension
 Whis's pocket dimension.
The Time Nest
The Time Nest is the 4th dimension and where all the multiverse's history is kept and time is created by Tokitoki, the god, creator, and embodiment of time. It's Chronoa's job as the Kaioshin of Time to record history and watch over the time flow of the multiverse. If the vault is destroyed all history will be erased. There is only one Time Nest and it is located on the edge of Universe 7.
 Time doesn't exist in Otherworld.
 The History of Ever.
 Effects like Ginyu's Body Change is undone if you return to the Time Nest.
 The Time Vault is literally part of or is the multiverse, as the windows integrated into it are gateways to timelines and if it is destroyed the multiverse will be erased.
 Xenoverse refers to Tokitoki City as a "Xenoverse", which means Alien or Unkown Space.
 Fusion lasts forever in Tokitoki World.
The Crack of Time
The Crack of Time is an extra-dimensional space that transcends the multiverse. This
space is outside of, houses, and is interconnected to all timelines. Due to the fact it transcends both the Time Nest and multiverse it is a 5th dimensional space.
 Chronoa states it is a space separate from the dimension of Time.
 The Crack of Time's bottom in Heroes.
 Dokkan states it is the gap between history
 An official scan states it is beyond time and space.
 In Heroes Chronoa states it's outside of Time.
 Towa states it is the space between dimensions.
The Over World
The Over World is a metafictional place in Dragon Ball Heroes that is a fictional version of our world. The Over World transcends the Heroes multiverse and the people of the real world have to use avatars of themselves and a dimensional transfer machine to interact with it. Because it transcends the Crack of Time it can be considered a 6th dimensional space.
 People in the real world view DBH as fictional.
 Salsa playing Ultimate Mission X on a 3DS.
 The people need to use a dimensional transfer machine to enter.
 Trunks states it's a higher dimension as the Dark Energy transcended into Beat's world.
When beings from the Real World enter the DBH multiverse, they become avatars. 
Verses and Other Places in the Multiverse
 Dragon Ball Fusions, Jaco the Galactic Patrolman, Dragon Ball Z(Including Filler), Dragon Ball GT, Dragon Ball Budokai, One Piece, One Piece Gold, Dragon Ball Minus, Dragon Ball Super, Dokkan Battle, Yamcha Reincarnated, Dragon Ball Online, Dragon Ball Extreme Butoden, Broly God, Dragon Ball 4d, All Dragon Ball Movies
 World of Void, a place outside the multiverse with no time or space.
 Unknown Void outside history
 Time Ring Void in Universe 10 which holds Time Rings.
 The gateway between timelines in Dragon Ball Super.
 Omni-fused world made by Shenron.
 Teleportation Dimension
 The World of Mind Control and mental planes of existence.
 Parallel Quest title says it is a multiverse.
 Official XV2 Scan.
 Fu states history isn't finite.
 A time patroller said history can take infinite possibilities.
 Fu states there is a multiverse.
 Beerus states there is a multiverse.
 Multiverse Theory in the manga and anime.
- Both multiverses have been destroyed at least once. By Demigra then by Zeno.
- Great Priest is currently the strongest fighter in the multiverse, Goku is the strongest mortal, and Zeno is the strongest being(Excluding Tori-Bot).
- The existence of a multiverse was first hinted at in Dragon Ball Shin Budokai by Cell.
- All 12 universes are apart of one timeline
- The Chasm of Time is similar to the Mirror Cave in Pokemon and the Caverns of Time in World of Warcraft.