KaiOS Product is decoupled into two components : Core and App Profile.
The underlying platform that consists of the Web application runtime, i.e. Gecko, plus the hardware adaptation layer and a few other supporting module.
A collection of built-in web apps, which represents the user interfacing functions of KaiOS for a given device form factor.
Additionally a set of core components including file and memory management, threads and data structures etc. are provided through the XPCOM component object model.