Continuous Delivery is a software Engineering approach where:
- Software is developed in short cycles
- Incremental updates to application in production
- Automate delivery, bring together different processes & execute quicker.
Note that Continuous Deployment means that every change is automatically deployed to production, but Continuous Delivery means that the team ensures every change can be deployed to production, but may choose not to.
Summery: In order for Continuous Deployment one must be doing Continuous Delivery