Galaxy Note4: What is private mode and how to use it?
Use the Private mode to prevent others from using or accessing specific content, such as images and documents, stored on the device. You can activate this mode, save content to a specific location, and then deactivate private mode to hide items securely.
Private mode is available for the applications of Gallery , Video, Music, Voice Recorder, My files and S Note.
How to Set the Private Model?
Alternatively, open the notifications panel or the quick setting panel, and tap Private mode to activate it.