One of the major pet-peeves of Drupal developers (and developers of other popular CMSes for that matter) has always been the way configuration is handled and deployed from one environment to the next. Drupal 7 stored most of its configuration in the database, so various solutions had to be concocted by developers to get that moved up the latter as development progressed.

In Drupal 8, great advancements have been made in this respect with the introduction of a centralized configuration system that although stores all configuration in the database, allows it all to be exported into YML files (and then reimported). So, from a development point of view, we have it much easier now if certain features depend on configuration (for example, a new Field).

Configuration is also of two kinds--simple and complex (configuration entities we noted in the Entities section). The difference between the two is that the former is always singular in that it stores just a value (or multiple values together), once--the site name and email address, for example. You only have one site name. The latter, on the other hand, represents multiple instances of the same configuration type, for example, multiple View definitions or multiple entity bundles. In this book, we will see a bit of both.