These are papers that are examining a topic from the past (probably years), and then providing new insights, a review, or new data/experiments/whatever that puts the old stuff in a new light. As pretty much all scienctific papers are in the business of "new insights", one might ask the question why does such a thing like "revisiting" paper even exist. In some fields there are certain topics that have been neglected, for various reasons. Then it is appropriate to do something like this. Usually the people who write a "revisiting" paper are experts in the field with years of experience.
Revising a paper
Just an ordinary process of peer review, that (almsot) every paper goes through. You submit a paper to a journal, it goes to review, and comes back with a list of issues the reviewers had. You revise the paper in order to address the issues and make the paper suitable for publication.
Both of these things are unrelated to your wish to split your research into two papers or more.
Some of the criteria to decide whether to split you research are:
- Is the research in its current "one paper" form too long compared to other similar papers in similar journals?
- Are there several main ideas in the research that each one can be in a paper of its own?
- Is the research such that different aspects of it are relevant to researchers in different fields, such that it is appropriate for publication in different journals?
If you want to split your research just for the sake of having more papers, do not do it. It's called "salami slicing" (see the other answer here) and is usually frowned upon because it is a waste of everybody's time.