The left area of the status bar describes actions of menu items as you use the arrow keys to navigate through menus. This area similarly shows messages that describe the actions of toolbar buttons when the mouse pointer stays over them a little while. This message is also shown as you depress a toolbar button, before releasing it. If after viewing the description of the toolbar button command you wish not to execute the command, then release the mouse button while the pointer is off the toolbar button.
The right areas of the status bar show the number of the current simulation step or indicate which of the following keys are latched down: