to be more explicit: "System" are files from the original language pack, provided by the core or extension developer, containing all translatable files. Using "host" or "site" option, a superuser or admin may adjust text for his own usage in all portals or current portal only, which don't get overwritten on upgrades (!). Typical examples are Terms of Use and Privacy Statement, which should always be adopted to reflect the use case of the current site.

thanks Sebastien

So, regarding upgrades are you referring to upgrading the lang pack?  And thus saying that the site and host sections don't get upgraded if I install a new lang pack version?

Also, would I be right in assuming that none of these gets overwritten when dnn is upgraded?  I have had a situation before where a resource file was overwritten when a module was upgraded. I am keen to avoid this kind of problem in the future.

thanks
Rach