XML primer for this lesson. No parser was run.

An element has a name and content:
  <room>east</room>

An attribute sits on the start tag:
  <room id="4">east</room>

An internal entity is a name the document itself defines:
  <!ENTITY club "desk">
  <room>&club;</room>
Predicted expansion if internal entities are enabled: <room>desk</room>
That expansion was not observed.

An external entity would name a resource outside the document.
This file does not declare one, and it does not name a file or a network address.