Multiversal travel is a general term for the various methods of travelling between universes. As the Omniverse is made up of more than three spatial dimensions -- the exact number is uncertain -- it is extremely difficult and risky to actually navigate a multiverse itself. This means one cannot simply visit any universe that exists, and travelers are most often confined to visiting known universes and discovering new, nearby universes by random.
If a new universe is visited, it will frequently be one that shares some sort of a cluster with the originating universe, which means they are likely to share very similar laws of physics and species at least resembling those found on the originating planet. However, this can depend on the multiverse or even the cluster, as different ones may have different laws regarding multiversal travel.
Discussed here are known methods of multiversal travel within the known multiverses.
The use of portals to hop to other universes is popular, because if a planet in another universe has already been visited many times previously, a portal leading to that planet can be easily opened with the use of magic or technology. This happens because of the presence of a portal wormhole in the multiverse, which links both planets together. The ends of the wormhole are attracted to major sources of gravity such as planets and are affected by the flow of time, causing the two universes to have a shared timeline. Eventually, the web of portal wormholes connecting multiple universes together effectively forms a multiversal cluster.
Generally the endpoints of the wormholes will stabilize and begin to engulf the entire planet with use, especially as events are shared between the two planets. This often means a portal leading to a specific, frequented universe can be opened at any point on the planet. A planet can have multiple portal wormholes engulfing it.
Travelling through a portal wormhole is instantaneous, and one is able to see and hear the other universe merely by looking through the portal, as photons and sound energy will hit the portal's surface and be instantly transported to the other side. Gases will instantly travel through a portal as well, if measures are not taken to shield the portal from the air pressure difference.