currently I am on a data structure book called data structure and algorithms made easy in

java, in that book(page 291), there is a discussion about finding cut vertexes in a given graph. but I have hard time to understand the concept. even I google about it and try to figure out. but not able to understand.. already I wasted 2 days on it... any body has idea about it? if yes, could you please explain?

Note: I understand the definition about cut vertex