This is a text varbind, accessible only through notifications, carrying supplemental free-form details about whatever alarm condition triggered the trap. It gives the receiving network management station or alarm log extra context beyond the trap's basic OID and severity, such as the specific reading or location involved. For example, a trap for a low-battery-voltage alarm might carry trapInfo text like "Battery string 2: 42.1V" to tell the operator exactly which string and reading caused it.