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Help is available from several sources, each one useful to you in different circumstances:
You don’t need to be connected to the Internet to view Help in Lightroom. However, with an active Internet connection, you can access the most up-to-date information.
Help in the application: The complete user documentation for Adobe Photoshop Lightroom is available from the Help menu, in the form of HTML content that displays in the Adobe Community Help application. Even without the Community Help application, this content will display in your default browser. This documentation provides quick access to summarized information on common tasks and concepts, and can be especially useful if you are new to Lightroom or if you are not connected to the Internet.