Artifact repository
A versioned store for build outputs, compiled binaries, container images, packages, that sits between the build and the deployment so the exact artifact that was tested is the one that ships. Artifact repositories such as container and package registries give builds immutability and provenance: you deploy a specific signed version rather than rebuilding from source.
An artifact repository is the system of record for build outputs, the exact, versioned, immutable binaries that get deployed. It matters because "rebuild from source and hope it's identical" is not a reproducibility strategy: dependencies move, toolchains drift, and the thing you ship should be the thing you tested. Promoting one signed artifact through environments, rather than rebuilding per stage, is what makes a release auditable and a rollback trustworthy.