Creating a Release Bundle creates an immutable and signed set of content with a specified version identifier. After the Release Bundle has been created, it can be promoted to different environments with full traceability (see Promote a Release Bundle to a Target Environment).
Release Bundles are created in the platform UI from one or more existing builds (including aggregated builds) or from existing Release Bundles.
In addition to the options available in the UI, Release Bundles can be created from a list of artifacts or from an AQL query using REST APIs. See Create Release Bundle Version.