The document discusses PHP Documentor, a tool for generating documentation from PHP source code. It can output documentation in HTML, PDF, CHM and XML formats. PHP Documentor recognizes JavaDoc-style tags in comments and generates class inheritance diagrams. It is customizable through templates, allows linking between documentation sets, and can parse various file types like README and CHANGELOG. The document provides an example of using PHP Documentor and installation instructions through PEAR or from source code.