And container is a component , where I am using a Redux state inside of a React component. Because note, while we have the application state in redux store, but here in this component I am again declaring some states.
Why Container Component - To separate our data-fetching and rendering concerns. A container does data fetching and then renders its corresponding sub-component.
The container component that knows about redux and dispatch and store and state.
The wrapped-component (i.e. which is not a container) in the pattern, which does the rendering doesn't need to know about any of that stuff: it gets its method to call via its props.
And ... mapDispatchToProps was the useful means that redux provides to let the container-component easily pass that function into the wrapped component on its props.
The Container is a file that corresponds directly to a single component. Think of it like a literal container that you put your component in to ‘upgrade’ it. By using two container functions called mapDispatchToProps and mapStateToProps, you can now link up your component’s props to state and action dispatchers (which are used to change state). If you had a div in your component that you want to display a property of state, you can simply make that div display a prop and then use mapStateToProps to link up that prop to state. If you want your component to store something in state, you can create a prop, call it as a function, and then use mapDispatchToProps to dispatch an action.
https://medium.com/@holtkam2/react-redux-understanding-the-data-flow-fd700b6bd56f