When you see a folder icon on a button, it means that when you select that button it will load another board into view. This is how CoughDrop lets you access more than just the number of buttons that would reasonably fit on a single screen.
When you hit a button that takes you to a new board you can always go back to the previous by hitting the "Back" button in CoughDrop. Or the "Home" button will take you back to your home board. Also, depending on your user preferences, hitting a non-folder button may automatically return you to your home board.