Correct. MC won't launch without a Library. The Library includes not just imported files, but almost everything you "see" onscreen when you open MC including:
* All Library Views in the Tree, in Theater View, and in the Media Network (JRemote/Panel/etc).
* All playlists and smart lists.
* Podcasts.
* A number of "hidden" databases, including previously seen files (things imported once, but then removed from MC), Optical Disc database, TV Recording schedules, and a variety of other similar items.
And a Library Backup includes all of this, and also includes ALL the settings on the system: the DSP Settings, everything in Tools > Options, Zones, and even the Library Manager (including the "setup for" all of the other Libraries your system might know about).
Not only can you restore them to other machines, in oder to "clone" your setup from one machine to another, they even work cross-platform. So if you want to move (or clone) from a Windows copy of MC to a Mac copy of MC? Same deal. Backup on one, restore on the other. In most cases when you do this, you'll need to then re-import all of your files or fix them with find-and-replace in RMCF (because the filesystem is very different, and file paths won't match) but, you can still get 85% of the way there with a Library Restore).