In software engineering, continuous integration (CI) is the practice of merging all developer working copies to a shared mainline several times a day. - https://en.wikipedia.org/wiki/Continuous_integration
Continuous delivery (CD) is a software engineering approach in which teams produce software in short cycles - https://en.wikipedia.org/wiki/Continuous_delivery
Continuous deployment (CD) is a software engineering approach in which software functionalities are delivered frequently through automated deployments. - https://en.wikipedia.org/wiki/Continuous_deployment