The Metaverse in this context is a continuously updated digital copy of the real world, where the "environment" is generated passively by users.

Imagine a city park where a handful of people have glasses with cameras on them that are continuously sending a geo-located feed of the images to a map server which processes it into a 3D reconstruction. You could watch in real time as the city park is reconstructed and updated in real time 3D, add in virtual content, make content "layers" for different digital assets, track interactions etc...

It's a globally crowdsourced, consistently updated real time digital twin of the world.