Expansion pack - I see it as an expansion of the sim's lifestyle adding a lot basic normal life things in one themed pack. Usually there's more than one new system or they're bigger than game packs.
Game pack - An experience of specific gameplay with things that are made to a target audience. Technically a fanservice pack.
Stuff pack - A great collection of clothes AND objects, with new animations, and luckily a skill with new animations and interactions.
Kits - A much smaller collection of clothes OR objects that are complements to expansions and game packs. Basically a half-stuff pack without any chance of new animations and interactions.
