This question was VTCd once as a duplicate, and then promptly closed by the Community bot. Ordinarily one would need four votes for the question to be closed. Alternatively, it would require the voter to possess a gold badge in the tag, which isn't the case here.
If there are pending votes or flags to close a question as a duplicate of a certain target question, the question owner can indirectly bindingly close the question as a duplicate of that target (the Community user will cast the actual vote)
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 a close vote again on that question).