In the Marvel Universe, the terms "multiverse," "megaverse," and "omniverse" are used to describe different levels of existence and reality.
Multiverse: The multiverse refers to the existence of multiple parallel universes within the Marvel Universe. Each universe exists independently with its own set of physical laws, timelines, and variations of characters and events. These universes can have subtle or significant differences from each other. Examples of known universes in the Marvel multiverse include Earth-616 (the primary Marvel Universe), Earth-1610 (the Ultimate Universe), and Earth-199999 (the Marvel Cinematic Universe).
Megaverse: The term "megaverse" is not extensively used in Marvel comics, but it can be understood as a higher level of reality that encompasses multiple multiverses. While the specifics may vary, the concept suggests that there are different multiverses coexisting within a larger framework or structure.
Omniverse: The omniverse is the highest level of existence in the Marvel Universe. It includes everything that exists, encompassing all possible realities, multiverses, and dimensions. The omniverse transcends the concept of time and space and contains all possible iterations and variations of the Marvel Universe. It is considered the ultimate level of reality, representing the totality of all existence.
It's worth noting that the precise definitions and usage of these terms can vary depending on specific storylines, writers, and interpretations within the Marvel comics. Marvel has a complex cosmology, and these concepts are used to explore the vastness and diversity of its fictional universe.