Enter some text into the "New Item" field. The same text will then be added to both the Queue and the Stack. You can see both lists grow as you add items. Notice how the queue and stack add the item differently.

You can also remove items from both lists by clicking on the "Remove/Pop" button. You'll see the lists get shorter, and you'll also see the removed item appear at the bottom.

By adding and removing items you should be able to see both the Queue and Stack in action.