The repeat mode for your current playlist is a three-way toggle between the following options:
No Repeat (Grey Circular Arrows): Play through your current playlist and then stop after the last song.
Repeat On (Blue Circular Arrows): Play through your current playlist and then restart the playlist after the last song.
Repeat Song (Blue Circular Arrows w/ Number 1): Repeats current song over and over until switched from.
This option is located at the bottom of the Play Queue listing in the Now Playing Screen.
For Windows and OS X users, select Repeat None, Repeat One or Repeat All from the Player pull down menu.