Definition of 'Active' and 'Passive' use of Ablilities

[Nedorus]

In another thread (concerning Walls and Power Parries) the point came up, that

the character actively using their powers; the idea for Walls doing it seems more passive

In trying to understand this I came across:

Originally Posted by P168 DEFENDING WITH POWERS

Power Block counts as an active use of the defending ability, even if that ability is normally passive.

Now I'm wondering what exactly constitutes an "active use" and a "passive use"? and where I would find the "definition".

I'm roughly aware that some abilities (like Detect) need some maneuver or concentration to be used and others (like Danger Sense) do NOT require this. So the former might be classified as "active" the later as "passive".

However the above quote from Powers seems to suggest that there is a more formal definition. Or is there?