Closed vs Resolved

Currently when we put a date in the Actual Completion Date field the system marks the issue as "Closed" and I've been told there's no way to change this. However, we have resolution of an Issue set up to show as "Resolved". So when we utilize the Mark As Done feature it marks the issue as "Resolved" as it's supposed to. There's a difference between Closed and Resolved. It would be nice if the system recognized both features and they both resorted to the same resolution type. It's confusing and requires a learning curve to teach users.