Why did the North want to blockade southern ports? And how would this help the Union win the Cvil war?

One reason was to block the South from receiving any resources that would help them to continue fighting in the war. They were trying to force the South to stop fighting so they could get more resources. This helps the Union when the civil war by forcing the South to surrender, or by giving them a reason to make an effort end the war as well.

an informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.