The spiral notebook is where we hold the scanned pages. The last page is an empty page with three kinds of sources.  "Single Scan" presents the system default camera view, and you can take a picture, that is the most straight forward way of adding scans.  "Continuous Scan" presents a customized camera view that is used for taking pictures automatically. It takes a picture after a pre-defined timer expires, saves the image immediately, and then fires the timer again.  It is very useful for scanning books. In this use case,  iPhone is usually held by some mechanical arms, the book is positioned under the camera, and you turns the pages manually.  "Add from Album" lets you pick a photo from your photo album.  Tap on the "+" icon on the toolbar will always bring you to this page so that you can start to add scans. For people who might be interested in previous version (1.x), we are including a screenshot here.  You can see that the interface was very primitive at that time.  Some people actually prefer this style.  To me, one of the drawbacks is that if we are to add more sources, there simply isn't enough space.