I was writing a new paper in my office, when an e-mail arrived telling that my second last paper had been reviewed.
When you want your paper to be published in a scientific journal, unless you are asked, the paper need to be reviewed by a couple of scientific professionals, who read the paper and give questions and comments to you. If they do not like the paper, it could simply be rejected. The authors must answer to the questions and comments and revise the paper accordingly.
My reviewers were in favor of my manuscript, so I did not have to change much. Even though, it took some time to change one figure and the manuscript. I sent the new paper to the co-authors. After their approval, I will send it to the publisher. Hopefully, the paper will be accepted this time for the publication. The paper will appear on the web first and will be published in the printed journal.
When I was in college, papers, comment, questions, and answers were delivered by snail mails. I even drew figures manually. Now, everything goes on the web using PCs. It became easier but a bit busier.