[yk]

There are several different "multiverse" ideas, from the top of my head the many worlds interpretation of QM, the string landscape, the multiverse of general relativity, the multiple branes in Randall-Sudrum models.

Thing is, multiverse ideas are not testable and therefore not physics. Theorists like to entertain ourselves with them to a certain degree, but they are just that, a kind of Science Fiction. For that reason, theorists never bother to distinguish between the different kinds of multiverses, that is a tedious and ultimately not important task.

Now science writers love to write about the multiverse, because they are good entertainment, however they lack the technical sophistication to actually distinguish between the different kinds of multiverse.