You may check their allowed values in online help.
FORM_STATUS agregates block statuses: If none of them contains records - it's NEW, if at least 1 is changed - it's CHANGED, otherwise - it's QUERY.
MODE defines current operation. When you're entering query criterium, it's ENTER-QUERY, when the query is being executed, it's QUERY. Otherwise (entering/viewing data) - it'sNORMAL.
Regards, Dima