Continuous Integration is a term/buzzword that seems to have a clear understanding. Continuous Delivery and Continuous Deployment on the other hand, seem to get incorrectly interchanged.
Continuously integrate changes into source control in order to test changes through automated builds and unit tests. This provides developers with early warnings of broken code/merges and allows them to fix problems continuously.
Some have the opinion that continuous delivery is when you deliver to a user base, such as UAT or QA. I personally disagree. Continuous delivery is about making sure your software is always production ready.
via Jez Humble (The guy who wrote the book… literally)
In the world of continuous delivery, developers aren’t done with a feature when they hand some code over to testers, or when the feature is “QA passed”. They are done when it is working in production.
There could be situations or reasons why you might not want or cannot deploy every good build to production. However the idea is that every build could be released to production.
This implies continuous integration and higher level of automated testing. It also allows Dev Ops and others outside of the development life cycle the ability to determine when to deploy to production.
This takes continuous delivery one step further by automating deployment to a production environment. This implies continuous integration and continuous delivery.