This means you can now explore and "try out" in a shared playground (*) the new API features that have been added to Community 201711 (6.0.0-ea) and ACS 5.2.2. These include new Audit and Avatar API's.
(*) Please be aware that (as always) this is a publicly accessible & shared demo server. Please do not upload private, sensitive or valuable data. The server is not backed-up and may be reset or taken offline without warning.