Continuous Integration (CI) is the practice of merging code frequently and automatically building and testing every change. Continuous Delivery (CD) extends this so every passing change is automatically prepared for release, and Continuous Deployment goes one step further by automatically pushing every passing change to production without a manual approval.
For QA, CI/CD reframes testing from a phase at the end of development into a continuous, automated activity that runs on every change. In CI, each push triggers a build plus fast automated tests, so integration bugs surface within minutes instead of during a big-bang merge. Continuous Delivery keeps the software in an always-releasable state — the pipeline runs the full test suite and packages a deployable artifact, but a human decides when to release. Continuous Deployment removes that human gate: if the pipeline is green, the change ships automatically, which demands very high confidence in the test suite. The distinction matters in interviews because 'CD' is ambiguous — being precise about Delivery vs Deployment signals maturity.
A team practicing Continuous Delivery merges 20 PRs a day; each runs the full suite and produces a deployable artifact, but a release manager clicks 'deploy' once a day. A more mature team switches to Continuous Deployment: because their tests are trusted, each green merge deploys itself within minutes, and the release-manager step disappears.
Scenario: In an interview you say 'we do CI/CD'. The interviewer asks: 'Do you deploy every green build to production automatically, or does someone approve releases?' Why does this distinction matter, and how do you answer to show you understand it?
Never let 'CD' stay ambiguous in an interview — state whether you mean Delivery or Deployment; conflating them is a common junior tell.