'UserState' refers to a table in the application database (XFUserState) where the state information is stored. If you search for USERSTATE in the rules snippets you will get examples for the Get and Set. The information in UserState is available the next time the user logs in. If you just want the info stored for the session use Globals (globals.SetObject and globals.GetObject).
GetUserState and SetUserState are used in an OpenPlace application (Data Import Schedule Manager - DSM). Look in the Dashboard Extender DSM_SolutionHelper for complete functions that use them.
