implement simple insurance system using redux

action creator -> action -> dispatch -> reducer -> state

• action creator defines and returns action
• dispatch actions
• reducer processes the actions
• update state

• return an action (object)
• action consists of type and payload
• type is string to be distinguished by reducer
• payload is data

• distinguish action type, and process
• return state
• can be combined multiple reducers using combindeReducers

• store is state which consists of reducers
• managing state by dispatching actions (=> operate reducer)