The Sims 4 comes with two different worlds in which your Sims can reside, socialize, and explore. While each is similar in function, the two worlds have different themes. Willow Creek is designed with a New Orleans flavor and antebellum style architecture—especially in the venues and large, more expensive homes. Oasis Springs, on the other hand, is set out in a desert environment with a combination of southwestern and modern architecture. No matter where your Sims choose to live, they can easily travel between the two worlds.
The Sims 4 eGuide Tour of the Worlds