There's lots of types of multiverses; the conventional one where there's just multiple universes (Stage 1), the Bubble universes which contain stage 1 universes (stage 2), the ones predicted by string theory (10 to the power of 500 universes) and the Schrödinger's cat multiverse (using quantum theory).
Inflation predicts a multiverse as tiny quantum fluctuations were stretched during the FTL part of inflation so other universes could have been created.