The menu.
Main menu, secondary, tertiary and so forth.
It is a good idea to plan your sections and sub sections in advance when writing your content, this is often easiest to categorise by department, try not to have too many main menu sections. Make sure each sub section fits intuitively under the main menu, don’t force things.
A planner will order your menus to their best advantage, making sure that dynamic content such as register forms and account features are intuitively and fluidly positioned within the menu structure.