This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
Then a better approach would be to learn more about Apache. That would enable you to understand that document better. Getting a "more precise" explanation isn't going to help if you don't know much about Apache.