# Core concepts Core concepts explain the internal structure of HedgeDoc by providing background information and explanations. They are especially useful for contributing to HedgeDoc. <!-- markdownlint-disable no-inline-html --> <div class='topic-container'> <a href='/concepts/notes/'> <div class='topic'> <span>📝</span> <span>Notes</span> </div> </a> <a href='/concepts/user-profiles/'> <div class='topic'> <span>🙎</span> <span>User Profiles</span> </div> </a> <a href='/concepts/config/'> <div class='topic'> <span>🛠️</span> <span>Config</span> </div> </a> <a href='/concepts/api-auth/'> <div class='topic'> <span>🤖️</span> <span>API Auth</span> </div> </a> <a href='/concepts/events/'> <div class='topic'> <span>🎩</span> <span>Events</span> </div> </a> </div> <!-- markdownlint-enable no-inline-html -->