Structs

A MusicBrainz release represents the unique release (i.e. issuing) of a product on a specific date with specific release information such as the country, label, barcode and packaging. If you walk into a store and purchase an album or single, they are each represented in MusicBrainz as one release.
A track is the way a recording is represented on a particular release (or, more exactly, on a particular medium).

Enums

The type of packaging of a MusicBrainz release entity. Note that this enum is non_exhaustive; The list of release types is subject to change and these changes are only reflected in the DB, not in actual MB code. Variants are derived from the release_packaging table in the MusicBrainz database.
The script used to write the release’s track list. The possible values are taken from the ISO 15924 standard.
The release status describes how “official” a release is. Note that this enum is non_exhaustive; The list of release types is subject to change and these changes are only reflected in the DB, not in actual MB code. Variants are derived from the release_status table in the MusicBrainz database.