The difference between transient and detached objects, those are as below:
Transient objects do not have association with the databases and session objects. They are simple objects and not persisted to the database. Once the last reference is lost, that means the object itself is lost. And of course , garbage collected. The commits and rollbacks will have no effects on these objects. They can become into persistent objects through the save method calls of Session object.
The detached object have corresponding entries in the database. These are persistent and not connected to the Session object. These objects have the synchronized data with the database when the session was closed. Since then, the change may be done in the database which makes this object stale. The detached object can be reattached after certain time to another object in order to become persistent again.