Unification of the One Buddha Śākyamuni

[T]he Sutra says that innumerable Buddhas or duplicates of Śākyamuni in the worlds of the ten directions were assembled in one place. Each of the duplicates can be seen as a manifestation of Śākyamuni himself, who took the forms of other Buddhas in order to expound the Dharma in other worlds. Now they were all assembled in one place, meaning that all the Buddhas throughout space were unified at that moment by the one Buddha Śākyamuni.

Introduction to the Lotus Sutra