Docker images serve as pre-built packages containing all necessary files and dependencies for running software within Docker containers, which provide consistent and isolated environments across various host systems. These images employ a layered file structure that allows for efficient sharing, reuse, and updating, with each layer uniquely identified by a DiffID. Docker uses a storage driver, such as Overlay2, to manage these image layers and their writable counterparts on the host machine. The article elaborates on the internal structure of Docker images, detailing how the images are stored, identified, and managed, utilizing identifiers like ImageID, ChainID, and CacheID to ensure integrity and facilitate caching. Developers can inspect these layers and their attributes using commands like `docker inspect`, enhancing their understanding of Docker's image management. The piece also highlights the benefits of using Earthly for optimizing Docker builds, thus improving productivity and efficiency in managing containerized applications.