Knights of Tezoth

A defensive action is performed during an opponent's turn and does not consume an action, nor does it require the presence of a commander in the unit.

I still don't understand how it works...

What does "does not consume an action" mean? So a figure with defense can, outside its own turn, defend a city it is in and also perform another action on its own turn?

Can a unit have no Knight and consist solely of units? Or what does "presence of a commander is not required" mean?

If a city is attacked, those capable of defending it can do so any number of times.
It can consist solely of units, and then it can only defend.

In short. City X of faction Y is attacked. In city X, there is a unit of figure Z with a defense action. The battle begins, and figure Z participates in it regardless of whether it performed any action during faction Y's turn. When it becomes faction Y's turn, figure Z can perform any of its actions despite having been involved in the defense. Did I understand correctly?🤔