It's no groundbreaking news for anyone anymore: Drupal 8's database agnostic and it comes with a drastically improved core entity API. This allows it to interact with remote data stored in pretty much any type of external database. In this respect, there's a whole array of contributed modules that you can use for retrieving and integrating external content into your Drupal website. Now the new challenge that arises is: what if you wanted to display that external data as... Drupal entities? And this is precisely where the Drupal 8 External Entities module steps in!