4+1 dimensionality, means, that Multiverse has 4 space dimensions, and 1 time dimension. here you can't understand true form of this -verse, just because our 3-dimensional eyes isn't prepared to observe 4-dimensional objects.
Multiple Universes. Really many of them. Multiverses diameter is so large, that it's incalculable by human technology, so, an unknown number of Universes lies beyond ours.
Different Concepts Edit
Multiple Universes Concept Edit
The Time Worm Concept Edit
Multiverse is like our Universes, repeated infinite ammount of times, forming an infinite... kind of... "worm". And we are currently just a replay of already recorded Universe.