By a funny coincidence, the abbreviation CD can mean two different things. The concepts of continuous delivery and Continuous deployment are pretty similar, but they have some subtle differences. Throughout the book, we are focusing on the concept of continuous deployment. This is the automated process that originates when a person pushes a change into the central repository and finishes with the change successfully deployed to the production environment with all the tests passing. We can therefore say that this is an end-to-end process as the developer's work travels all the way to the customer without manual intervention (following the code review, of course). You may have heard the term GitOps to relate to such an approach. As all operations are automated, pushing to a specified branch in Git triggers the deployment scripts.
Continuous delivery doesn't go that far. Like CD, it features a pipeline able to release the final product...