Pending
The package preparation has not yet started.
That status allows cancels.
Processing
The package preparation has started. It is not possible to make cancels anymore.
Processed
The package preparation is done, and it is ready to be sent.
Sent
The package has been given to the carrier. If that's possible, more information (such as the carrier itself, a tracking number, …) will be delivered too.
That status allows returns.
Received
The carrier sent us an information that the package has arrived at its destination.
That status allows returns.
Digital products are always set on “received”
Unknown
That status is no good. It may mean that the status has been lost. You should contact the carrier to have more information.
Cancelled
All the products of the package has been cancelled.