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 the asker (now by anyone), it will be added to the reopen queue. Other than this, there is no functional difference between “on hold” and “closed”.
Who can close a question?
- Users with at least 250 rep may vote to close their own questions
- Users with at least 3,000 (500 on Beta sites) may vote to close any questions (see limits below)
- Moderators may close any question (regardless of their reputation)
- The same users who can vote to close questions can also vote to reopen them
- Users can also retract/cancel their close vote by clicking the close button again and clicking the "Retract Vote" button (you can't cast close vote again on that question).
What are the limits for closing questions?
- Each user with vote to close privileges gets 24 votes to close per day (50 on Stack Overflow)
- 5 votes are required to close or reopen
- Votes will expire after 4 days if the question does not reach 5 votes
- Questions containing a bounty cannot be closed
- You can only vote to close once per question
- You can only vote to reopen once per question
What are the reasons for closing a question?
When closing a question, a reason must be provided for the action. Not all close reasons are available on all sites. If none of the reasons for closing the question apply, you should strongly reconsider voting to close.
Questions in these categories may be closed:
Exact duplicate: Questions that cover exactly the same ground as earlier questions on this topic should be closed. See How to handle duplicate questions?
Off-topic: Questions are generally expected to be on-topic for the site to which they were posted, within the scope defined by the community.
The “off-topic” option provides further guidance. Closers can either select a predefined message, or type in a custom explanation.
- Belongs on [another site]: Questions that are unrelated to the site topic, but would fit on another site in the Stack Exchange network.
Unclear what you're asking: The way the question is currenty written, it's hard to tell exactly what is being asked. The explanations in the question are not clear, or it is not clear what kind of answer is expected, or there is not enough information to solve the problem. The question may be reopened if it is clarified or if the missing information is provided.
Too broad: There are either too many possible answers, or good answers would be too long for a Q&A format. The question may be reopened if it is edited to focus on an issue that can be answered in a few paragraphs.
Primarily opinion-based: Many good questions generate some degree of opinion based on expert experience, but answers to some questions will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise.
Is closure the end of the road for a question?
Definitely not. Closed questions can and should be edited to improve them and address the reasons why they were closed in the first place. Once this is done you might need to either flag the question for moderator attention or raise a meta question to bring it to everyone's attention so it can get the necessary views that might translate into reopen votes.
It's only when a question can't be salvaged that it should move onto the next state - deletion.
When are closed questions eligible for deletion?
Closed questions become eligible for deletion by the community after 48 hours, but users with 20K reputation or more are not subject to this restriction. See here for the rules governing question deletion. See also Do closed questions ever get deleted?