If you look at network devices as clients and devices that received SNMP traps or poll devices as servers then the community string is the same as apassword that the server issues to the client device during a remote query. The string can be just about anything reasonable, as long as the client and the server use the same community strings.

Most network devices allow different levels of SNMP access, for example: READ ONLY or READ/WRITE. Each one of these levels of access would/should have a different (hard to guess) community string.

When a client sends an SNMP trap to a server receiving SNMP trap information, the SNMP community string is not required.

However, some devices use the SNMP community string as a password for terminal (serial and monitor) access to the device as well. Don't just change them and forget them

That is just about it........ the poster stated that the device was only sending traps, so the community string is not so important between client-server (no server queries to the client device) but should be changed for security reasons so something other than the default value, i.e. public.... Make sure you document the change somewhere safe so if you forget to tell the next responsible person after you leave the project, they will have a roadmap of the changes you made!

However, never fear... most SNMP community strings can be reset from the console/monitor of the device (or with physical access to the device). Yet, if you have hundreds of devices..... depending on this technique (physical access to reset) is not a good idea