Mathematics
Looking into the math library, you will find classes for 2d, 3d and 4d vectors. The engine and the engines interface make heavy use of these classes, so you should get familiar with their methodes.
To define a 3d scene with objects in it, you need a world coordinate system, which is fixed in space.
Relative to the world coordinate system other coordinate systems are used, which define a 3d objects
position and orientation.
A very important class is the Frame. Frames control an objects position and orientation in 3d space.
Using a frame you can transform 3d objects and cameras. (also see the documentation about the camera).
The frame can be thought of as a 3d coordinate system. A 3d coordinate system is defined by its origin and the
three coordinate axis. The origin positions the coordinate system and the three axis define the aiming.
The picture on the right shows a 3d object (teapot) and its frame. The frame is placed at the bottom of the teapot. Translating the frames origin gives the teapot a new position. Rotating the frame defines a new orientation.