# Domain Driven Design: Domain Layer

Domain Layer contains business objects and the core (domain) business rules of the application and it's the heart of the application. Here, is the list of building blocks of the Domain Layer:

* [Entities & Aggregate Roots](./entities.md)
* [Value Objects](./value-objects.md)
* [Repositories](./repositories.md)
* [Domain Services](./domain-services.md)
* [Specifications](./specifications.md)