Question library is a collection of reusable questions. One question library may contain many questions, all questions can be edited and deleted and new questions can be added either from the administration screen (resources -> question library) for question library or by clicking on the "To lib" link when you edit a survey question.
Editing a question in a library is similar to editing a question in a survey; same question types, attributes and export/import functions are available. See Questions for more information.
All Opinio administrators can create question libraries. Other users need an administrator to grant them such access, as they can not create question libraries by default. See user profile for more information. Administrators can also grant and restrict access to existing question libraries.