I'm not an expert in HP-UX, but in general, these things are talking about SNMP version 1 "community names", which are (a bit like) passwords, although they're passed around in clear text, so aren't really like any other passwords you might be familiar with.
Whenever you send a get request in SNMP, the request has a community name attached to it: if this community name matches the get community name specifed at the agent end (that is, in your snmpd.conf), then all is well.
Similarly for SNMP set requests.
You can test if the entries work by and changing the community names in snmpd.conf, and then attempting get and set operations on any MIBs that you have installed.
For a few examples of how this works with net-snmp (and open-source SNMP agent implementation) see
www.net-snmp.org, but do bear in mind that (since I'm not an HP-UX expert (nor indeed an SNMP expert!)) the details may vary with your local stuff.