Basically, the metaverse (metaverse) is a virtual world, which takes place parallel to the physical world. So a virtual parallel universe. The special thing about it is the decentralization. Everybody can participate in the construction, network with others and move in it.
It is like a gigantic computer game, but one that is closely linked to our reality. e.g. via IoT (objects that function in both worlds or in cryptocurrencies that have an equivalent value in reality e.g. Bitcoin, Nft, Ethereum, etc.).
Technologically, the Metaverse is built on virtual and augmented reality and takes place in a 3D virtual space. This combines the various capabilities of the Internet into a shared virtual universe. In the words of Mark Zuckerberg: "The Metaverse is no longer just the Internet you look at. It's something you participate in, move around in."
While Meta CEO Mark Zuckerberg is talking about the metaverse as the next big thing on the Internet in 2021, there were initial moves in that direction as early as 1980. Sci-fi author William Gibson was already talking about Cyberspace back then, while Neal Stephenson first mentioned the metaverse as a term in his 1991 science fiction novel "Snow Crash."