Logging 172.x.x.x :asks the router to send log messages generated by router to one syslog server that has the IP 172.x.x.x
SNMP Server host 172.x.x.x Public :asks the router to send SNMP traps (events)generated by router to one SNMP server that has the IP 172.x.x.x using the community name (like a password): public.
note it is recommanded to change the defaut community name from public to a new one.