Q: What does the status 'in press' mean?
You have not mentioned the previous statuses that your manuscript went through. This would have helped me give a more specific answer. Generally speaking, the status "in press" appears after the paper has been accepted for publication. It means that your paper is now in the final stages of production. If you have not yet received the page proofs, you will receive them soon. If you have already submitted the corrected proofs, your paper will be ready for publication soon.
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