nightwalker

Actions, Reducers etc are tiny concepts that come under Redux indicating how Redux works.

When you're asked Why u need X? in interviews, you'd generally state the problem first, explain the how X comes out as a solution and then comes -- where all you use this X in your application (which is your answer) unless interviewer is expecting a single line of answer.

Having said that above, The fundamental answer for Why you need Redux? is not something out of the box genius answer. It's straightforward; Component State's scope is restricted to the same component level hence accessing/watching a property of Component's state by other Components is not possible in a direct way. One of the approaches is props passing where you pass data(from parent to child) and parent-functions(from child to parent). This approach becomes unmanageable when the interaction between components grow, specially if both the interacting components aren't near to each other in the component hierarchy. And the other approach is sharing a common state between the interacting components so that the Producer component affects its data on the same state container on which Consumer component is listening to. This approach is followed by Redux and Redux manages it on the application/global level....then your Redux definition.. and finally the places where you'd use it..

This level of elaboration might be too much or less, depending on the interviewer but yeah, this would be my brief answer for Why do we need Redux if one liner of Global State Management for Components is not suffice for them.