The shuffle mode for your current playlist is a toggle between the following options:
No Shuffle (Grey Crossed Arrows): Play through your current playlist as it has been established or saved.
Shuffle On (Blue Crossed Arrows): Randomizes the current playlist, including the current song and insert point.
The shuffle button scrambles your current playlist randomly each time, so deactivating and reactivating the shuffle option will re-scramble your currently active playlist each time.
While active, The option also pre-scrambles any playlist you add to your current queue.
For smartphone users, this option is located at the bottom of the Play Queue, in list mode on the Now Playing Screen.
For tablet users, this option is located at the bottom of the Play queue on the right of the Home Screen.
For Windows and OS X users, select Shuffle On from the Player pull down menu.