Along the right side of the front panel there are four LEDs and a small three-position switch. As delivered, the LEDs and switches are connected to Vesta discrete inputs and outputs. There are also some simple rules defined that illuminate LEDs based on switch position. Try moving the switch and observe what happens to the LEDs and to the Vesta controller web interface.
This switch and these LEDs can be used for any desired purpose. In particular, they are good for developing and testing rules before assigning the rule to real hardware. The LEDs are often used as visual indicators of system status, and the switch can be used to manually set operating modes ('Summer' vs. 'Winter', for example).