The button bar (cont'd)

The Play button is used to run the Alice program and play the animation.

The Undo and Redo buttons have generally the same meanings as similar buttons in other Windows programs.

The Trash Can is used to dispose of things that you no longer need. 

The Clip Board is used for generally the same purpose as clip boards in other Windows programs.

(You can use one of the menu selections to add more clip boards if you need them.)