Basic structure of Drupal
Explains the Drupal codebase.
Core components are based on 3rd party libraries and other components.
Core subsystems are based on...
Resources
core_version_requirement
Specify supported core version in *.info.yml files.
Theme hooks vs module hooks
Some hooks can be used in themes.
Wim Leers
Wim Leers' blog.
Grav CMS for Drupal developers
This article maps Drupal concepts to Grav. Grav is a lightweight CMS that uses flat files instead of a database.
YAML for config...
Friday 5: 5 Command Line Tools You Should Use NOW
Brief intro to 5 useful tools. My eyes popped a few times after seeing how useful these are.
J-P Stacey
Blog by a freelance Drupal developer. Great articles!