Yep, sorry, it's probably a bit confusing. The whole design system is open-source, from its components to also the documentation. You can find it on the GitHub repository: https://github.com/kiwicom/orbit/tree/master/docs
But basically it's a system how to design and develop applications (mostly mobile or frontend). It contains most of the time some visual foundation, standardized components, guidelines etc.
It's fine if things are targeted! I don't expect all my technical documentation to fully namespace all their ambiguous terms in case a non-engineer shows up. This site is for [D]esigners and that's cool.