A fire danger rating (Moderate, High, Extreme, Catastrophic) describes how dangerous a fire would be if one started — it is a forecast, not a law. A Total Fire Ban (TOBAN) is a separate legal declaration made by the ACT Emergency Services Agency that prohibits most fires in the open for a declared period.
Australian Capital Territory also has a Fire Season, during which extra restrictions or permit requirements can apply even without a total fire ban (toban). Councils, parks and land managers can impose their own bans on top of state declarations.
For what you can and can't do — campfires, BBQs, machinery and permits — see the full ACT fire ban rules.