These are the companion files for Distributed Systems with Node.js, O'Reilly 2020. These files aren't required to follow along with the book; the book contains everything you need to recreate them. However, they're provided here as a convenience.
If you can't get a program to run you may find that by looking at these files you've made a typo. Or, you may find that one day an npm package update causes an incompatibility in your program, at which point a package-lock.json file in here may help you out.