Schema files are required in order to define how configuration objects are structured and how (and if) Drupal should handle translation of configuration data. They are used to ensure that configuration data is loaded and saved in the correct data type, so developers don't need to worry about casting the values into the types they need.

If the data types provided by Drupal do not fit your needs, you can simply extend those types by creating your own.

With all this knowledge about configuration objects and configuration schemas, we will learn how to add configuration to custom modules in the next chapter.