The term "metaverse", still new to ordinary people, is now actively discussed by tech companies, marketers and analysts, who call it the future of the internet, BBC reports.
The concept is attracting the attention and money of many tech giants, including Facebook and Epic Games.
We explain what it is, what investments are being made and what form the technology takes today.
Outwardly, it looks like a more advanced version of virtual reality (VR), but many are convinced that the metaverse is the future.
The metaverse and VR technology relate roughly the way a modern smartphone relates to the first mobile phones of the 1980s.
Instead of a computer, the metaverse offers, with the help of a VR headset, to immerse oneself in a virtual world that will combine digital environments.
Unlike today's virtual reality, which is used mainly for games, this virtual world can be used for almost anything: work conferences, games, concerts, watching films, or simply relaxing.
In this world, people will be able to exist as their own 3D avatar. But since this is still only a concept, there is no single agreed definition of the metaverse yet.
Hype around digital worlds and augmented reality appears every few years, but usually fades.
This time, however, the idea of the metaverse has stirred wealthy investors and large technology companies. If it turns out to be the future of the internet, no one wants to be left behind.
And for the first time, the technological component and advances in VR gaming seem ready to make such a project a reality.
Facebook has made building the metaverse one of its priorities.
The tech giant is investing considerable sums in development, accessible through the Oculus headset, although some analysts consider these investments unprofitable.
The social network is also developing VR programs for virtual meetings and work conferences, including ones that interact with the real world.
Facebook says the metaverse "will not be built by one company overnight". The corporation promises to cooperate with other companies.
Recently it invested $50 million to fund non-profit groups to help "build the metaverse responsibly".
However, according to Facebook, the idea of the metaverse can be realized no sooner than in 10-15 years.
Tim Sweeney, head of Epic Games, which produces the game Fortnite, has long discussed the idea of the metaverse.
Multiplayer online games have used interactive worlds for many decades. This is not quite the metaverse, but there is some resemblance.
In recent years Fortnite has expanded its product, hosting concerts, brand events and more in its own digital world. Its capabilities have impressed many and drawn attention to the concept of the metaverse that Sweeney has talked about.
Other games are also approaching the idea of the metaverse. For example, Roblox — a platform for thousands of individual games connected within a large ecosystem.
At the same time, Unity, a platform for developing 3D games, is investing in "digital twins", digital copies of the real world. And the graphics company Nvidia is building its Omniverse, which it describes as a platform for connecting virtual 3D worlds.
Although there are many concepts of what the metaverse should be, most of them are based on human interaction. Thus, the application of the technology is not limited to the gaming sphere.
Facebook, for example, has experimented with a virtual reality meeting app called Workplace and a social space called Horizons. Both programs are based on virtual avatar systems.

The Workplace app combines virtual reality with the use of regular computers.
Another app, VRChat, is entirely focused on online communication and chat, with the sole goal of exploring the virtual environment and meeting people.
Recently, Tim Sweeney told the Washington Post that he imagines a world in which a car manufacturer, promoting its new model, "launches it in a virtual universe, and anyone can take it for a drive".
Or, for example, you go shopping online and, before ordering something, try on clothes in a digital environment.
In recent years virtual reality technology has taken a big step forward. High-quality headsets have appeared that realistically reproduce the player's movements in virtual space.
The technology has also become more widespread: for example, the Oculus Quest 2 gaming VR headset was a popular Christmas gift in 2020.
The surge of interest in NFTs, which can provide reliable tracking of ownership of digital goods, already shows how the virtual economy will develop.
More advanced digital worlds will require high-quality and more consistent connectivity, such as 5G technology. For now, all of this is at an early stage.
The evolution of the metaverse, if it happens at all, will take place among tech giants over the next decade, and perhaps even longer.