Flatpak
Flatpak is a software package system for Linux, which is supported by a wide variousity of distributions and provide features like isolated environments (so called sandboxes) or creating your own repository for your applications. Flatpak is mainly used for graphical applications.
Concepts
Runtime - Applications do not run directly in your OS, they are isolated in Sandboxes. For each application, a so called runtime is chosen. Those runtimes are a base, which can be used by multiple applications. This base contains dependencies, libraries and other requirements the app needs to be executed.
Sandbox
Repository
Build a Flatpak bundle
TODO