Here are the classes, structs, unions and interfaces with brief descriptions:

Block	A definition of a Minecraft block.
Box	Defines a full 3D box to be rendered.
Colorb	Defines an RGBA, 32-bit color. Each element is a byte (valued 0 - 255, inclusive).
Face	Defines a 3D plane for rendering.
IBlockRenderer	An interface to a block renderer.
ITexture	Interface to a texture. Specific to scripts: this is just an opaque handle to a texture. You cannot modify or access any members of this, as these are handled by the program.
ModuleInfo	A structure for defining information about this module.
Point2	A 2D generic point. Specific to scripts: this generic type is not exposed, only the typedefs are.
Point3	A 3D generic point. Specific to scripts: this generic type is not exposed, only the typedefs are.
RendererBase	The base class for renderers.
Schematic	The interface to a schematic file, which allows access to block data for this schematic.