This is where you go to take a picture of a bill, or to load a bill image from a file. If you have upgraded to the Professional Edition, you can also choose to scan the image and extract the data using OCR (optical character recognition). Because the scanning is done by a web service DivisiBill first converts an imported picture to gray scale and a lower resolution to minimize the amount of unnecessary data that is sent to that service.
Tap on a highlighted area to see what it does (on a desktop browser you can also hover over an area to see its name).