As far as I understand this tool works at higher level - with directories and files.
I will try to explain the concept less accurately. For example, you have your favorite os versioned in git. (kernel, x server, apps, init daemon, session management...). This tool will take all the stuff, compile it, will create directory structure and place binaries to appropriate places. In the end it will create bootable directory structure (filesystem tree) to that you can chroot. But maybe you want to test different revision of systemd. So ostree will take chosen revision from git, compile it, add binaries to filesystem while preserve old structure. It will add only new things that are different. Both verisons will be bootable. It's basically binary mapping of git tree.
in the past when ubuntu was still "linux for human beings" they did great job polishing the linux and providing good linux experience. They were very good improvers.
but then they decided to became inventors. But they don't have strong engineering background and their products were trash.
upstart never provided advanced parallelism and was surpassed by systemd
Top menu and indicators rely on d-bus -- really stupid idea and misuse of technology
they abandon mutter+clutter for closed gl-canvas rendering library + compiz to be used in unity. Now is mutter+clutter far more advanced.
Now they want to change wayland for mir? are they serious? They are not good at inventing things. They will just make linux fragmentation much worst. It's really problematic to make good drivers and gpu companies can't spend money and people on different linux platforms.
ubuntu became from "linux for human beings" to "crappy mac-os like for poor"