just in short:
SolarWinds Trap Service - handling device Traps messages
SolarWinds Syslog Service - handling device Syslog messages
SolarWinds Orion Module Engine - interact with MS Database and reads/writes polling data there.
Solarwinds Information Service (v1 v2) - can interact with persistence storages (not just MS SQL) and mainly reads data from there.
SolarWinds NetFlow service - NPM NetFlow module specific service.
SolarWinds Job Engine (v1 v2 v3) - data processing service. Usually does a device polling (icmp, snmp).
SolarWinds Collector Services - responsible for polling data processing and requests. Prepares data for the persistence storage.
SolarWinds Alerting Engine - processes all the alerts (those which you can see on web console for instance) for every SolarWinds product.
Let us know if you are looking for something specific.
Thanks a lot.
What about JMX bridge ?