What is a deployment environment (dev, staging, prod) in CI/CD?

Deployment environments are separate infrastructure contexts that represent different stages of the software delivery lifecycle. Development (dev): where developers test their own changes in isolation, often on local machines or ephemeral cloud environments created per branch (preview environments). Staging: a production-like environment where integrated changes are tested — runs the same infrastructure configuration as production but with test data; acceptance tests, performance tests, and UAT (User Acceptance Testing) happen here. Production (prod): the live environment serving real users, with real data; changes arrive only after passing all previous stages. Some organizations add a QA environment between dev and staging. Environment promotion — moving the same artifact from dev → staging → prod — is the core of Continuous Delivery and ensures that what is tested is exactly what ships.