In order to make it easier to determine which functions are currently available on the Autodesk control surface panels, you can select Mid from amongst the options accessible from the Navigation panel.
An active button is one that has been enabled by the user. For example, if you enable secondary two for Inside grading, the 2 button on the numeric keypad and the Inside button are backlit on the Navigation panel.
An available button is one that has been enabled by the system based on a feature that you selected. For example, if you switch from the Geom menu to the Reposition menu, the backlighting on the Function panel changes to show which buttons are available for performing repositioning tasks.