When a user first places an order the state will be 'new' which I understand makes the order non visible.
Given this state we can assign statuses like 'new' and 'pending' which I believe makes the order visible.
If the order's payment method is set to 'auth & capture' or if either 'invoice' or 'ship' is completed for an order but not both then the state will be 'processing`.
For such orders, statuses can be 'shipped' or 'invoiced'.
If both are completed then the state will be
completed as will the status.
So my doubt is how magento understand particular state is
is there any event-observer functionality for this?
I mean if user clicks place order button any observer will trigger?
Is there any definition for each state?