We will be building a module that replaces Kohana's own view layer (Kohana_View). It will use the PHP template library Twig. We want our own view layer to be API compatible with Kohana's view layer. This will ensure that other modules work out of the box and that the only code the developer will need to alter in their application are the templates (so that they are Twig compatible). No code in any controller will need to be modified.
They lay out the directory structure (dropping all files in /modules) and show you how to enable the module. He talks a bit about what Twig is and shows the code needed to initialize it and configure some of its basic settings. They define the "capture()" method and include a sample of using Twig in your controller.