The toolbar performs the following operations:
Add and delete real and complex poles and zeros
Zoom in and out
Invoke the SISO Design Tool's context-sensitive help
You can use the tool tips feature to find out what a particular icon does. Just place your mouse over the icon in question, and you will see a brief description of what it does.
Once you've selected an icon, your mouse stays in that mode until you press the icon again.
You can reach all of these options from the right-click menus.