This is the human-readable error text that accompanies the numeric remote-invocation error code for this object's state machine. Deleting a QoS definition isn't instantaneous — UCS Manager has to unwind every reference to it on every fabric interconnect and adapter that used it, and this task object is what tracks that cleanup to completion. An example value would be something like 'Failed to configure QoS class on fabric interconnect: resource unavailable', which is far more actionable to a network admin than the bare error code alone.