any doc / anyone who can explain SNMP parameters properly?

HI MTs,
https://help.mikrotik.com/docs/display/ROS/SNMP is driving me nuts as

  1. trap-generators do not contain all options
  2. trap-interfaces, means interfaces that can generate a trap, so what about the CPU???
  3. trap-target, is that necessary?
    Only if I want to receive agent-side generate messages?
    These are only the options in trap-generators:
  4. interface up or down
  5. smnp server starter up
  6. overtemperature