This is the human-readable error text that accompanies the numeric remote-invocation error code for this object's state machine. This is the policy object a vNIC or vHBA template points to; it's what UCS Manager pushes down through the fabric interconnects to shape and prioritize that interface's outbound traffic. 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.