Welcome to the filesystem example.
The resource "FilesystemResource" in filesystem.php is wired to any URI starting /filesystem and then maps the remaining part of the URI to the filenames on the filesystem within "examples/filesystem/representations".
This page is being read from "examples/filesystem/default.html" on the filesystem as it is the default document for the current URL. You'll also be able to see it at this URL.
The FilesystemResource also allows updating of the files by sending PUT and DELETE requests to their mapped URI.
The resource "FilesystemCollection" in filesystemcollection.php
View a collection resource for the directory "examples/filesystem/representations/collection".
The FilesystemCollection also allows adding of a file to the collection by sending a POST request to the collection URI.