Let's take a look at the three principles of Redux:

• Single source of truth: This means that the whole application state is stored in a single object. In a real app, this object is likely to contain a complex tree of nested objects.
• The state is read-only: This means that the state can't be directly changed. In Redux, the only way to change the state is to dispatch what's called the action.
• Changes are made with pure functions: The functions that are responsible for changing the state are called reducers.

Redux shines when many components need access to the same data because the state and its interactions are stored in a single place. Having the state read-only and only updatable with a function makes the interactions easier to understand and debug. It is particularly useful when many components are interacting with the state and some of the interactions are asynchronous.

In the following sections, we'll dive into actions and reducers a little more, along with the thing that manages them, which is called a store.