The objective is to provide end users with the modifications that have been made to the application as soon as possible. So continuous delivery and continuous deployment can be interpreted as applying the concept of continuous integration to the deployment of applications.
It is important to keep in mind that continuous delivery does not consist of deploying each change in Production as soon as possible, but that each change must be available to be deployed at any time.
It begins once the application is built and must be deployed in the following lifecycle environments. For example, deliver the new version of the application for QA so you can perform the tests and finally deliver it to Operations so you can do your implementation in Production.
The paradigm of both continuous delivery and continuous deployment is to automate as much as possible all the actions necessary to implement a new version of the application and all the necessary tasks to validate that new version. So every time you get a new version of the application from continuous integration, the release criteria for the next environment are validated and so on.
The main difference between continuous delivery and continuous deployment is that the first one requires manual approval before it is implemented in Production, while the second is even put into production automatically once all the criteria defined for the entry in Production for an application.