A “closed session” is where the Board meets privately, not open to the general association membership. It is sometimes called an Executive Session, similar to many City Councils and other government legislatures.
The authority to meet in private is granted by ARS 33-1804, but only items that meet the criteria of paragraph A (items 1 thru 5) can be discussed.
Note that “Discussion of a member’s appeal of any violation cited or penalty imposed by the association” can be discussed in an open session, at the request of the “affected member”.