For the community's dictionary

A Game Pack is one of three different downloadable contents for The Sims 4 that you can purchase through Origin or different stores selling them. 

It's a concept that came with The Sims 4 and it has been described as a mix between a Stuff Pack and an Expansion Pack. Too small to be an Expansion Pack, but too big and including too many new game features and content to simply be a Stuff Pack.

At the time of writing, there are currently 4 Game Packs released for The Sims 4: 

• Outdoor Retreat
• Spa Day
• Dine Out
• Vampires

Please note that you need The Sims 4 in order to use and play any of the Game Packs