A complimentary and/or purchaseable addition to a game which includes physical/digital content (i.e. artwork, audio, video, manuals, maps, etc.) These are most commonly included with physical media softwares, but CD Projekt has popularized them through their digital distribution platform at GOG.
The Witcher 3: Wild Hunt (GOG Version) includes a complimentary goodie pack.
Divinity: Original Sin 2 (GOG Version) includes a premium goodie pack, named "Divinity: Original Sin 2 - Divine Ascension."