The store is the central objects that holds the state of the application.
Learn Redux — Introduction To State Management With React
Sebastian Eschweiler
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The store might have been a great idea at the time when it was introduced, but by now it seems clear that it is merely a variant of a global state stream.

Only it is less powerful, lacking proper stream methods. And because it is so inflexible and harder to use, people resort to a single global store, where in reality, there is absolutely no reason to break your app’s encapsulation and keep the state of that tiny input field global.

And that is why the Redux official TodoMVC example is still using imperative state updates, the ones making your code impure, harder to test, ones that with proper data flow architecture should not be there:

https://github.com/reactjs/redux/blob/master/examples/todomvc/src/components/TodoTextInput.js#L23