burnsclass1980
The door is closed. You cannot go through. Closed means that option is no longer available. If something is closed you cannot do it. Closed is the opposite of open. A good metaphor for closed is a solid wall. Closed is not a door.
Understood means you get what the other person is saying. For example, if you are asked to do a task and you do it promptly, then you understand. Another example of understanding is when a teacher asks a question and you answer it correctly, that is understanding.