This is a node that is set up for the operator's convenience. It is up to the NC of a net whether the reason for the request for private node is a valid one. Normally, private nodes are for extenuating circumstances only. There are various FDN's. Ask your sysop for further information.
Users are the reason behind echomail, but users have no say in things.
Hubs count the same as sysops unless they hold an office. Up from there is the NC, Net Coordinator. This person is responsible for seeing that all the sysops conduct themselves in a manner becoming to FIDOnet, and to take action upon any that don't. The NC is assisted by the NEC, Net Echomail Coordinator. However, like users, we all know they exist.