State is what makes components interactive, and React gives you two hooks to manage it locally: useState for simple, independent values and useReducer for complex state with many related transitions. Choosing the right one keeps your components readable as their state grows from a single boolean to an interrelated object with structured update logic.
useState, introduced earlier, is perfect when state is a single value or a few unrelated ones, updated directly. But when several pieces of state change together, or updates follow complex rules, scattering many setState calls becomes hard to follow. useReducer consolidates all the update logic into one pure reducer function, making complex state predictable.
Both hooks store state local to a component instance and trigger a re-render when updated. The recurring discipline is immutability: you never mutate state in place; you produce a new value and hand it to the setter or return it from the reducer. This lesson covers both hooks, when to reach for each, and the immutable-update patterns they share.