Imagine being able to walk around inside your creation shown in the images and chat or have a voice conversation in real-time with several others. To be inside that 3D virtual reality without needing headgear - or even to create more 3D within that 3D environment or add a non-playing character to interact with as part of role-play, quiz, or simulation for a variety of purposes. All at a cost of almost nothing more than your connection to the Internet. It's actually quite popular with gamers as they look for more value beyond shoot em up gaming :) It adds the social component many felt was missing from engaging in 3D online. But, the software one downloads (free) to view and interact in these virtual worlds is so easy to use one need not be a gamer or even a graphic artist expert with things like Blender.
Open Simulator is an open source multi-user virtual world platform. It is used to create virtual worlds online (a group of them can be an Estate or a full grid of virtual worlds where a user creates an account and their assets are managed. Most of these grids agree to a Hypergrid protocol that allows users on each to not only communicate with each other but also allows their avatars to travel between them. It is a decentralized virtual world environment where people can socialize, create, fantasize, simulate, role-play, and more.
It is sort of like Second life but has far more capabilities like easily made interactive Non-Playing Characters, far lower costs, and the ability to self-host for those who venture down that path. Self-hosting can be complex so I don't recommend that until you at least have learned some basics on creating an avatar to represent yourself, learn to interact, learn to customize your avatar, learn to use the basic build tools, learn to use the advanced and developer menus, and learn to import mesh items like that shown in your images. For scifi fans, a good place to start might be on a non-profit Open Simulator grid called the 3rd Rock Grid which is the home of a Starfleet Role Play called Astraios Colony. If that interests you, I can help you get started there.