React is a popular JavaScript library used for building user interfaces. Redux, on the other hand, is a predictable state container for JavaScript apps. It provides a centralized place to manage the state of an application and makes it easier to create predictable, maintainable, and scalable code.

In Redux, the state of the application is stored in a single object called the store. The store is immutable and can only be updated by dispatching an action. An action is a plain JavaScript object that describes what change needs to be made to the state. Actions typically have a type property and an optional payload property containing data relevant to the action.

Reducers are functions that receive the current state and an action as parameters and return a new state. Reducers are the only way to update the state of the Redux store. They should be pure functions, meaning they should not modify the state directly, but create a new state object.

In React, you can use the useSelector hook to access the state stored in the Redux store and the useDispatch hook to dispatch actions to update the state. By using Redux, you can simplify your code and make it easier to reason about the state of your application.