1. Redux: Redux is a state management library for JavaScript applications. It provides a centralized store to manage application state and enables predictable state management by enforcing a strict unidirectional data flow. It also offers features like middleware, which can be used to handle asynchronous actions.

2. Redux Thunk: Redux Thunk is a middleware for Redux that enables the use of asynchronous actions. With Redux Thunk, you can dispatch functions instead of plain objects as actions. These functions can then perform asynchronous operations and dispatch regular actions once the operation is complete. Here's an example:

// Action creator that returns a function (thunk)
const fetchUsers = () => {
  return (dispatch) => {
    dispatch({ type: 'FETCH_USERS_START' });
    fetch('/users')
      .then((response) => response.json())
      .then((users) => dispatch({ type: 'FETCH_USERS_SUCCESS', payload: users }))
      .catch((error) => dispatch({ type: 'FETCH_USERS_ERROR', payload: error }));
  };
};

1. Redux Saga: Redux Saga is another middleware for Redux that enables the use of asynchronous actions. With Redux Saga, you can use ES6 generators to define complex asynchronous flows. It provides a set of powerful APIs for managing side effects and handling complex scenarios such as race conditions and cancellations. Here's an example:

// Saga that watches for FETCH_USERS_REQUEST actions
function* fetchUsersSaga() {
  yield takeLatest('FETCH_USERS_REQUEST', function* () {
    try {
      const users = yield call(fetch, '/users');
      yield put({ type: 'FETCH_USERS_SUCCESS', payload: users });
    } catch (error) {
      yield put({ type: 'FETCH_USERS_ERROR', payload: error });
    }
  });
}

So, when should you use Redux, Redux Thunk, or Redux Saga?

• Redux is the basic library for state management in Redux-based applications. You can use it for simple use cases or if you don't need to handle complex asynchronous flows.

• Redux Thunk is a good choice if you need to handle simple asynchronous operations, such as fetching data from a server.

• Redux Saga is a good choice if you need to handle complex asynchronous flows or side effects, such as handling race conditions or cancellations, or interacting with external APIs.

In summary, if your application needs to handle complex asynchronous flows or side effects, use Redux Saga. If your application only needs to handle simple asynchronous operations, use Redux Thunk. If you don't need to handle asynchronous operations, use basic Redux.