Configuration is the data that the proper functioning of an application relies upon. It is those bits of information that describe how things need to behave and helps control what code does. In other words, it configures the system to behave in a certain way with the expectation that it could also configure it to behave in a different way. To this end, configuration can be as simple as a toggle (turning something on or off) or as complicated as containing hundreds of parameters that describe an entire process.

The Drupal 8 configuration system is nothing short of a revolution in the Drupal world. It is not an improvement--it is a brand new way of thinking about managing configuration. Previously, there was no configuration management to speak of. Everything was stored in the database in a way that made it impossible to properly and consistently deploy the many configuration options that Drupal is known for. Yes, there was the Features module and the Ctools exportable, but their very existence highlighted that lack of consistency and this meant many a headache for lots of Drupal developers.

In Drupal 8, the entire thing has been revamped into a well-defined and consistent subsystem, upon which any little thing that needs to be configured can depend. Far be it for me to call it perfect, it still has its shortcomings and there is work in progress on making it better and creating tools for dealing with specific configuration flows. However, it has made managing and deploying configuration so much easier, as we will see in this subchapter.