Instant On gives the option to automatically turn the light on when you start the application.

Instant Off gives the option to quit the application when you turn the light off.

In its default configuration, when you start the application, you see that the light is off.  Then, with a flick of the switch, you will see the light turn on.  It will not automatically turn on unless you set this in the Instant On/Off preferences.

Instant Off is a great option if you want to minimize battery usage.  If you use it in combination with the Timer or A-Touch-Adds-Time, as soon as the timer runs out, it will shut your lite off and quit the application.