This dialog appears when you have dragged one or several modules from the Module Selection view to the Tree view. It displays the module type(s) and the location, where the modules will be added. Use it to confirm the insertion of the module(s). Yes confirms the insertion, No cancels it.
If you select this option and accept it with Yes, this dialog will not appear anymore in the future when you repeat this action. You can reactivate the confirmation dialog in the Tree view properties. By default, this dialog shows up.