This document summarizes key concepts about open documentation and community-generated content. It defines community as interactions within a group, discusses different types of communities, and explains that community comes before content. Community-generated content is defined as wiki-based documentation, comments, and forums. The document outlines why being open is important for participation, agility, and leverage. It describes the Mozilla Developer Network (MDN) as a resource for web developers that uses an open documentation model. Challenges of open documentation include getting people to contribute and ensuring accuracy. The document provides tips for avoiding pitfalls like intimidating new contributors and engaging a community.