The Simple Network Management Protocol (SNMP) is an application–layer protocol for exchanging management information between network devices. This is basically how most devices in a network communicate. In this, the most commonly used SNMP messages are the SNMP Traps. SNMP traps are alerts generated by agents on a managed device. To know more about processing these SNMP Traps, click here.
VarBinds are alert data incorporated into SNMP traps, that are sent to the SNMP manager. This data is encrypted and is contained in a typical key-value pair configuration. These key-value pairs are called "Variable Bindings" or in other words, VarBinds. Each VarBind is made up of a triplet (OID, Data type, Data value).
Example:
VarBind oid: 1.3.2.4.5.3.4.2.5.1.3.4 type: string value: DeviceDown