The container is the reflection of the data definition configuration. It is split into configuration sections. Each section is a small couple of configuration options, that belongs to each other.
For example, the Basic section contains basic container settings like the mode and data provider names. The Legacy view section contains all view settings related to the old dca format that is used in Contao.
Each DcGeneral instance can only handle one data definition container.
The container is created when the DcGeneral get created through the DcGeneralFactory. In the create event processing, multiple builders get triggered and fill the container with the sections. Different to Contao, the data definition must not defined in a DCA. The definition source depends on the builder. For example MetaModels use a custom builder, that fill the container directly from the database.
You find the default section interfaces and implementations in the DcGeneral\DataDefinition\Section namespace.
The Basic section contains the basic general configuration of the container.
The Data provider section contains the data provider configuration of the container.
The Legacy view section contains the view configuration of the container, provided by the old dca format.