I’m talking about the remote dev environments. Editing inside VMs, inside WSL, inside Docker containers or via SSH to remote machines, where the editing environment runs seamlessly on the remote, can have extensions, can do version control, run language servers etc.

https://code.visualstudio.com/docs/remote/remote-overview

Basically a part of the editor is running remotely, and yet can be managed as if it were local (e.g. an extension can be installed locally or into the remote). So your code is operated on entirely by the remote.

It is, as far as I am aware, unique in its scope.