Continuous Deployment - aka CD - is Continuous Delivery on steroids, in that it automates the triggering of the release of the builds that were created in Continuous Integration to all environments, including production. Without any human interference.
That makes Continuous Deployment also a Continuous Release with the asterisk that deployment (rolling out) != release (making available). But why have CR when you can have CD twice?
The automatically executed Automated Release connects both ends of the design => develop => test => deploy cycle of each iteration with a Feedback Loop.
- Wikipedia: Continuous deployment
- Atlassian: Continuous integration vs. continuous delivery vs. continuous deployment