Key point
One idea
When you render a list, React needs a key for each item. Use a stable string or number from the data, like an id, so React can track items when the list changes.
A key only needs to be unique among its siblings. It does not need to be globally unique across your whole app.
Why keys matter
React renders lists with normal JavaScript. Most of the time, you will use array.map() to turn data into JSX.
If you add, remove, or reorder items, React uses keys to understand what changed. Without good keys, React may reuse the wrong row and show confusing UI, especially when each row later has inputs or local state.