The whole X-Forge Game Engine consists of three main components called core, util and engine. This version of X-Forge provides the core and util components. The engine component is available for a separate license.
The core is the platform that hides the hardware and OS and provides services for the game engine and game applications, such as 2D and 3D graphics, audio and networking. The engine is the actual game engine layer, which provides an object model to a game world, physics, collision detection etc. With this version of X-Forge the game developer writes its own game engine on top of the core. Util is a collection of classes not required by the core, but useful for games and the game engine.
The source code and include files are organized so that there are sub directories called xfcore and xfutil under the source and include directories. All core class files, enums and defines are prefixed with XFc (enums and defines, being all uppercase, are prefixed with XFC). For util classes, the prefix is XFu and XFU and for the game engine, it is XFe and XFE.
Just like X-Forge itself is divided into three parts, so is the API reference.
Engine API Reference (available in full X-Forge Game Engine edition)