Menus: Home - Go Race - Cars - Tune - Customize - Options
Go Race: Career - Free Play - Test Drive - Multiplayer - Leagues - Rivals
Career: Continue Career - Stories of Motorsport - Showcases
Stories of Motorsport: Select a volume themed around a type of car
Volume: Select a series seems to be based on location
Location: Select a car division also based on car type
Showcases: race types such as Autocross, Spec, Stig, Track Day, Passing Challenge, Endurance
Pic of Mod Slots
Source: http://unwire.hk/2015/06/19/forza-6-preview/game-channel/