The basic idea of Redux is that the entire application state is kept in a single store. The store is simply a javascript object. The only way to change the state is by firing actions from your application and then writing reducers for these actions that modify the state. The entire state transition is kept inside reducers and should not have any side-effects.
Redux is based on the idea that there should be only a single source of truth for your application state, be it UI state like which tab is active or Data state like the user profile details.
All of these data is retained by redux in a closure that redux calls a store . It also provides us a recipe of creating the said store, namely createStore(x).
The createStore function accepts another function, x as an argument. The passed in function is responsible for returning the state of the application at that point in time, which is then persisted in the store. This passed in function is known as the reduce
