This is what I refer to as Viewfinder Mode. You can swipe up or down to alter the aspect ratio, or swipe left or right to change the filters. I will now explain the functions of the icons on the screen.
Change Mode
When you click on the switch button located at the bottom-left corner, you'll enter what I call 'Camera Mode'. In this mode, you can switch between different vintage filters to achieve that classic style in your photos.