Everyone has the same goal in a good IT organization: Put out the best applications and services on stable, sustainable infrastructure. DevOps helps keep that goal on track with continuous integration and delivery.
While developers focus on what's new and next, operations prefers stability and consistency. DevOps is a methodology or culture of IT wherein developers and operations teams frequently communicate about and collaborate on application and service releases. Many modern IT shops expect systems administrators, developers and infrastructure managers to implement continuous integration and continuous delivery.
Continuous integration means that iterative software changes are immediately tested and added to the larger code base. If a change creates issues, such as runaway storage use, that problem can be isolated and rolled back quickly.
Continuous delivery takes committed changes to the code and shepherds them through peer review and user acceptance testing. It is an extension of continuous integration. While many DevOps tools are designed to bring code through both CI and CD, in practice developers and operations teams use different tools in different ways.
Another CD term, continuous deployment, is a goal for DevOps organizations, though often fraught with real-world complications. Continuous delivery means that changes to the application or service are ready to be deployed because they are tested in a production-like environment. Meanwhile, continuous deployment means these changes go straight to production without awaiting human intervention.