GNOME OS has traditionally been a virtual machine image for testing, but with the work done by Codethink and other GNOME developers it’s becoming possible to run GNOME OS on bare metal hardware. Additionally, thanks to the likes of Flatpak and OSTree, it’s becoming more like a working Linux distribution in terms of package availability.
GNOME OS is part of the project’s continual testing investment and can be booted on real systems with UEFI via systemd-boot, systemd is leveraged throughout, Flatpak is available for a broad application base, Wayland and XWayland are utilized, the latest Mesa drivers are present, and OSTree provides atomic updates.
GNOME OS seems similar to KDE Neon, and I think it’s a great idea. It allows GNOME developers and users to easily test the latest and great versions of their software, without being dependent on distributions.