Most papers undergo revisions before acceptance. If a reviewer has recommended revisions, authors will then need to re-submit their manuscript having made appropriate changes.
If minor changes were requested, these are typically assessed by the editor.
If significant revisions were requested, the editor will usually return the manuscript to the original reviewers (unless they opted out of this). In some cases, a new reviewer may be invited. The editor should explain why this is necessary, and the new reviewer must respect the previous feedback and revisions made by the author.
The primary aim of reviewing a revised manuscript is to confirm that the changes requested during the initial review have been adequately addressed. Reviewing a revised manuscript should generally be faster than the initial review, as the main task is to check that the required changes have been made. Occasionally, new issues may arise, or the changes may not have been adequately implemented, which might require another round of revisions. Nevertheless, the aim of the review remains the same: to ensure the paper is of a publishable standard.
If you have been brought in to review a revised manuscript, editors usually provide the original decision letter and the author's response to that letter. This allows you to see the requested changes, including any suggestions from other reviewers, and how the author has addressed them.
Each journal has its own guidelines for how authors should identify changes they made in their revised manuscript. The most common method is for authors to highlight the changes in their revised manuscript.
If you have been assigned a revised manuscript review and still have questions, contact the journal’s editorial office.