Difference between Playlist and Folder

In the left panel under “Playlist” I can add “manual playlists”, “smart playlists” and “Folders”. What is the difference between a “Folder” and a “Playlist”? I can add new Playlists and can move albums into the playlist, but this is not working with the “folder”-option. How can albums put into folders?

Folder is to be intended as a playlists container , than you cannot put albums into a folder