Work item states
A work item passes through up to twelve states from intake to done. Transitions are enforced: an attempt to move to a state not in the allowed set returns an error.

The strip on a work item's detail page shows seven stages (Received, Triage, Plan, Approval, Execute, Review, Done). These are the visible milestones the UI groups the twelve underlying states into, not the states themselves.
State diagram
State reference
Allowed transitions
The full set of allowed transitions:
The four terminal states (completed, cancelled, rejected, duplicate) have no outbound transitions.
From the terminal
state= accepts any value from the State column in the table above.