Previously called the "QUAKE 3 Engine" and one of the most successful licensed engines in history, id Tech 3 was the engine used to create games such as Quake II Arena, Return to Castle Wolfenstein and Soldier of Fortune II: Double Helix. id Tech 3 introduced shaders, curved surfaces, 32-bit color, special effects, bleeding-edge networking and super-smooth speedy hardware rendering.
A level which will be compiled into a BSP is build with many different kinds of objects. With this tutorial the author intends to introduce these objects to the reader.
Finally, a mapping-for-dummies tutorial. Thanks to the author. :)
It is not a mapping tutorial :P , it explains the technological architecture behind the mapping process.
There are hundred of mapping tutorials, and this document shall be considered as additional literature to any mapping tutorial telling you how to do nice mapping.