This read-only DisplayString of up to 32 characters gives a human-readable description of what a particular CPD filter entry on a flow is matching. It's useful to an admin auditing flow filters because the surrounding CPD objects (Ethertype, subtype, MAC mask) are terse numeric fields, and this description is often the only quick way to tell what protocol the filter row targets without decoding those values. For example, a technician reviewing filters on a customer flow might see a description like 'CDP Filter' confirming that a given row governs Cisco Discovery Protocol frames rather than some other Layer 2 control protocol.