What does it mean for a question to be closed?
When a question is closed, no additional answers may be posted to it, although the question and existing answers can still be edited (by users with edit privileges or by suggested edit) and voted upon, and will continue to count for badges. The asker of a closed question may still accept an answer.
Closed questions can be re-opened by users who have sufficient reputation.
What does it mean for a question to be on hold?
If a question has been closed, then for the first 5 days, it is marked as “on hold” rather than “closed”. This is meant to convey that the question requires improvement and may be reopened if improved. During this period, if the question is edited by anyone, it will be added to the reopen queue. Other than this, there is no functional difference between “on hold” and “closed”.
