Continuous integration is a software development practice where developers regularly merge their code changes into the central repository (VCS). This activity triggers automated builds and tests to be run. The goal is to find bugs earlier, improve software quality and reduce time to validate and release new software updates.
Continuous delivery automates the entire software release process. Continuous delivery expands upon continuous integration by deploying all code changes to a testing environment and/or a production environment (only with approval) after the build stage.
Continuous Deployment – Very similar to Continuous delivery but there is an automatic deployment to production environment without any approval.
Continuous Testing is the process of executing automated tests as part of the software delivery pipeline in order to obtain feedback on the business risks associated with a software release candidate as rapidly as possible