It is your personal question library where you can add frequently needed questions. You can create and maintain your library from which questions can be easily added to any of your surveys.
You can access your question library under Surveys.My Question Library is only available under the My Surveys folder near the bottom right corner.
In your survey, click on the more (3 dot) menu and select the Copy To Library option. The question will get copied to your library.
In your survey, click on the Add Question button.
This feature/tools described here are available with the following license(s) :
Free License and above