Expansion packs (EP) are a kind of add-ons for games. They make the original game all the more interesting as it provides many new things to the game and are often centered around a theme. They require the original game (also known as base game) to work. Sometimes, collections of the base game and one or more expansion(s) are released called collections or compilations. The Sims 2 and The Sims 3 also offered mini-expansions called stuff packs (SP), which offered only new objects. Gamers are advised to check what every edition includes before buying.