What is the main setting in 4e?

Excuse me, could you elaborate on the main setting featured in the fourth edition of the game system you're referring to? Are we discussing a fantasy realm, a sci-fi universe, or perhaps a contemporary setting? I'm particularly interested in understanding the CORE environment that players are immersed in, as it can greatly influence the gameplay experience and narrative themes. Clarifying this detail would be quite helpful in grasping the overall essence of the 4e experience.