Murder vs Culpable Homicide: Unpacking the Gray Area

Hey fellow students, I've been struggling with this concept from the Evidence Act and need your help. In simpler terms, what is the exact difference between murder and culpable homicide? Textbooks explain it as a question of intent vs. negligence, but that's still not clear to me. Take the case of the Delhi gangrape case (Nirbhaya case): The convicts were charged with murder, but some people argued it was culpable homicide. How can we distinguish this in real-world scenarios? Is it just a matter of intent or is there more to it? Can someone explain it with a concrete example or analogy? Help me out, guys!