This is a simple gallery that is hidden behind a functional calculator. All you need to do is create a pin, then you will be able to access the gallery using the calculator. You have the option to delete the images, or videos, from your iPhones library when storing them to this gallery. Don't worry, you can add them back later if you need to. Once the images are stored in this gallery, and deleted from your iPhone library, they will not be shown in your iPhone library anymore.