One of the greatest tools for learning, is Tutor Mode. Tutor mode can be activated by clicking Settings->Options... and then click on the Tutor flag. Activate Tutor Mode by checking the Tutor mode check box.
The tutor window
In Tutor Mode, GNU Backgammon will analyze your moves and/or cube decisions and compare them with its choices. You set the threshold for its alerts, for example, if you set it for bad then it will only warn you when you make a bad mistake. It will then allow you to re-examine your choice, go right ahead with it, or provide a 'hint' - essentially, showing you its analysis.
The tutor can give warnings on both cube decisions and checker play. If you want the tutor to only warn on cube decisions, you can uncheck the box for the Checker play. Likewise, if you want it to only warn on checker play decisions, you can uncheck the box for the Cube decisions.
The tutor warning window
In the above figure, you can see a warning dialog from the tutor mode. If you press the button labeled Play anyway, the move you made will be kept and the game will continue. If you press the Rethink button, the dialog will close and the checkers that you moved will be returned to their original positions. You can then rethink the position and try an alternative move. Keep doing this until the Tutor accepts your move as being good enough. Alternatively you can press the Hint button to show the hint window with its list of possible moves and their evaluations. Finally, if you press the End Tutor Mode button, the dialog will close and turn Tutor Mode off.
A similar warning window will also appear for poor cube handling.