In this chapter, we described required insights in the post-implementation phases, primarily regarding the operational aspect of Docker containers. We started the chapter by clarifying important terms, such as images, containers, registry, and repository, in order to enable you to acquire an unambiguous understanding of the concepts illustrated thereafter. We explained how to search for images in the Docker repository. We also discussed the operation and handling of Docker containers, how to track changes inside containers, and how to control and housekeep containers. In the next chapter, we will explain promising and potential techniques and tools for building Docker images in an easy-to-grasp manner.