The Main Menu is made of 8 menus that allow the user to interact with Ardour, and below is a reference of all the menu actions.

Notice that a lot of this menus, and probably all of the most used ones have keyboard shortcuts to ease and fasten the work. A sum-up of these shortcuts can be found on the Defaults Keyboard Bindings page, and every menu in Ardour can be reassigned to an user defined key binding, or used via OSC with a control surface.