Various games are divided into two logical parts: engine and data. Often the engine and data are licensed in different ways, such that the engine can be distributed in Debian but the data cannot.
game-data-packager is a tool which builds .deb files for game data which cannot be distributed in Debian/Ubuntu
It is telling you what to do "Install game data for Quake" and that is what game-data-packager does - it builds the game data to a .deb file so you can install it
Developed by the award-winning id Software, Quake® is the ground-breaking, original dark fantasy first-person shooter that inspires today’s retro-style FPS games. With Quake (Enhanced), experience the authentic, updated, and visually enhanced version of the original.