For what it?
Hello, Sergey. This is referring to the project’s location in the resource hierarchy. When you create an "Organization" (which requires you to buy and validate a domain, which is why we haven’t done that in the course), you can have projects owned by the Organization and group them into folders for organization. You can read more about the GCP resource hierarchy at this link and this page describes how it can be used to securely manage access to your GCP resources.
I hope this helps!