A Build Package is the resulting artifact of a software build process. This can be, for example, a Docker image, a compressed archive file or anything else that encapsulates the whole software (component) including all (software) dependencies.
For executable software components - as oppose to libraries - the Build Package contains everything that is needed to run the software in a Runtime Environment. In that context a Build Package is especially intended can run in any available environment - be that resting, staging or production.
WIP
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