State

Summary

Data that a component owns and can change over time via `useState`, triggering a re-render whenever it's updated.

• 1Build a counter component to internalize how `useState` triggers re-renders.
• 2Learn why you should never mutate state directly — always use the setter.
• 3Practice the functional updater form (`setCount(c => c + 1)`) for state that depends on the previous value.