What's known as plugin or addon in other platforms, is what we call a module in the Drupal universe. Drupal core itself is a a collection of modules as well and the community has added and maintains tens of thousands of individual modules on top of that.
Keeping your Drupal modules aligned with the ever-evolving Drupal ecosystem is crucial for stability and maintainability. But manually testing module compatibility against various versions of Drupal core and other dependencies can be a time-consuming and error-prone process. Fortunately, Drupal offers a powerful solution: the GitLab CI Templates.
ECA stands for "Events - Conditions - Actions" and is a powerful, versatile, and user-friendly rules engine for Drupal 9+. The core module is a processor that validates and executes event-condition-action plugins.