A SNMP Trap is sent by a network equipment to the Network Monitoring Solution. Orion provides a way to collect/manage these Packets throught the SolarWinds SNMP Service and the Trap viewer.
An Orion NPM event is an entry in the internal log of the application. Events are mostly created when Orion NPM detects a change in the network status/topology. Advanced alerts can log NPM events as well.
Here is a list of the event types:
Critical System Error
Orion modules add further event types when you install them.