Modal Realism is a philosophical theory proposed by David Lewis that suggests all possible worlds are as real as the actual world we live in. According to this view, every way a situation could possibly be is represented by a distinct, fully realized world. These worlds exist independently and are not mere abstractions or fictions. In Modal Realism, when we talk about possibilities, we are referring to these concrete worlds. For example, if we consider a scenario where dinosaurs never went extinct, there exists a world where that is the case. This perspective challenges traditional views of possibility and reality, expanding our understanding of existence.