As confirmed in Boruto: Naruto the Movie, the Narutoverse is indeed a multiverse. Full of realms across different ages, it is a place not even fully explored by those who rule it, the Encompassing Federation. This organization seeks to rule and protect the multiverse which they preside over. In order to do this, the organization has set about researching and exploring the various realms to completely understand them, and to find any threats that could perhaps harm the multiverse as a whole.