The majority of Drupal sites living on the web are still built on Drupal 7.
While an amazing work has been done by the Drupal community to provide an upgrade path, more complex sites need to take a more refined approach and why not - improving the content structure, logic and avoid the mistakes done in Drupal 7 in the first instance.
This course is about breaking down a Drupal 7 site, rebuild and improve it in Drupal 9 after which the content is migrated and adjusted accordingly.
You’re expected to have at least some understanding of Drupal 7 main concepts, like Content Types, Entities, Vocabularies, and entity references.
Even if not, you might find it useful for understanding certain Drupal concepts and how to troubleshoot issues, as I bumped into a couple of them but solved afterwards.