What is the difference between "Abstract" and "Author Summary"?
For journals that have both, the abstract is typically intended to be a technical summary of the article for the core audience, while the author summary or popular summary is written in a less technical style and for a broader audience.
For the linked example, this is laid out in the journal's Submission guidelines:
We ask that all authors of research articles include a 150-200 word non-technical summary of the work as part of the manuscript to immediately follow the abstract. This text is subject to editorial change, should be written in the first-person voice, and should be distinct from the scientific abstract.