Have you ever wondered how to distinguish actually which Issues Statuses are Open and which Closed? For example, you got to the Issues list and select filter Status. There are values Open and Closed.
But let's also see the Issues list below. There are plenty of different statuses. How to know which are open and which are closed?
The key is to go to Administration - Issues Statuses. Here, you will find that the "closed" statuses are the ones with the option Issue closed enabled. All other ones are Open. You may check the below picture to make the situation clear: