react reducer what

Ok where is the general accepted implementation with react-redux. It is a global / subsection state management that maintain data used in your application. For example, lets say you have a Todo list, you might use, the following objects to keep track of it.

STATE {
- TODO_ID - when user click on ADD_TODO
- TODO_LIST - keep tracks of all your tasks you have created.
}


These are all trigger based on actions. This is why we have to setup actions. Action when someone click "Add Task". Then it sends a certain message - "ADD_TODO' to be specific to a  reducer.

What is a reducer?
Say you have fire up / dispatch / send out a 'ADD_TODO' instruction and you increment current task id with 1. So you can have a unique Id or some way to keep track of it. This is where you pass it to a reducer. You say hey, my ADD_TODO is fired, get me a new TASK_ID.

Reducer is where you are allowed to changes / update state STATE - TODO_ID.

Some other action will update TODO_LIST and so and so....

Then somewhere in time, you call connect() to tie store and action together.