ResetAppletState method in OpenUI applet class

I wonder how the method ResetAppletState works.

https://docs.oracle.com/cd/E14004_01/books/config_open_ui/appendix_a_API5.html#wp1372522

1) Method is bindable, but syntax is

oldActiveApplet.ResetAppletState();

So, I assume the applet must have a method? This method runs and bindable event run consecuently?

2) As I see, method runs when we click on another applet in view, or when we clear data and refresh BC. What is his real behaviour?

3) "The ResetAppletState method sets the applet to an active state if this applet is not active" - what does active state mean? Applet in a focus and the blue border around it? But I see method runs when we click out of the applet..