When will the draw() of Marker in de.fhpotsdam.unfolding.marker get automatically called

Question

I am working on Marker class in Unfolding library of Java and here is the API http://unfoldingmaps.org/javadoc/.

I noticed that the draw() is automatically called but I want to know: 1)What are the situations it will get called automatically 2)What are some details should be paid attention to it based on your experience?

I know the answer might include a lot of situation and I am totally welcome partial answers.

Thanks!