Why is the `key` prop important when rendering lists in React?

Imagine a classroom where every student has a name tag. When the teacher rearranges the seats, she can quickly find each student by their name — not by which seat number they were sitting in before. Without name tags, she'd have to guess who's who based on position, leading to mistakes. React's `key` prop is the name tag that tells React which item is which, even after the list is shuffled.