What has happened to my Side Bar in Finder?

All of a sudden since I turned my MacBook Pro on, the Side Bar in the "Finder" has changed and it does not list where I am keeping my files (Airdrops, Desktop, Downloads, Documents, etc.) It just shows location " My MacBook Pro". When I go into "Preferences" it shows all the listings to be used in sidebar. How could this have happened since I closed it down? How can I get this back to my original sidebar?