The basic difference between a metaverse and a multiverse is that:
A metaverse is a shared environment where shared activities like working, watching movies, playing sports, games, etc. are possible. On the other hand, the multiverse is an imaginary collection of virtual words with varying traits and features.
In a metaverse, there is only one shared universe where a user moves freely between different platforms. However, in a multiverse, a user is within a hypothetical pool of virtual words with many ecosystems.
Another distinguishing feature of a metaverse is the specific order of the flow of information. In a multiverse, no such specificity exists. It has a random flow of information through multiple universes.