Multiverse theory suggests that our universe is just one of many universes that exist simultaneously. These universes, often called parallel universes or alternate realities, may have different physical laws, constants, and even different versions of ourselves. The idea arises from various scientific theories, including quantum mechanics and cosmic inflation. In this framework, each universe can have its own unique properties and histories, leading to a vast array of possibilities. Some versions of multiverse theory propose that every decision creates a new universe, resulting in countless variations of events and outcomes. This concept challenges our understanding of reality and raises intriguing questions about existence.