What is the significance of the 'Multiverse' concept in Marvel and DC?

The Multiverse is a core element of both Marvel and DC, representing a vast collection of alternate realities. In Marvel, it's a constantly expanding and evolving concept, with stories exploring the consequences of altering reality. In DC, the Multiverse is often tied to the mythology of the DC Universe, with stories exploring the origins and connections between different dimensions and timelines. It's a key element of both universes' storytelling.