Rekit Core provides core functions for managing Rekit apps, it's used by both Rekit command line tools and Rekit Studio.
When a Rekit app is created, it has auto added rekit-core as a dependency. When you execute a command like 'rekit add feature f1' it finds the current installed rekit-core in the project to add a feature. So rekit-core is not global but project independent. Different Rekit apps may use different versions of rekit-core. This guarantees that the upgrade of rekit-core doesn't break existing Rekit apps potentially.
Rekit core APIs are well modularized and documented. It's the foundation for create custom Rekit plugins.
You can view the API docs at: http://rekit.js.org/api.
You can create your own plugins based on Rekit Core.