You can configure settings for layout, menus, headers and footers at either the SITE or SPACE level.
Generally speaking, you will see the same configurable settings for the site that you see in a space.
The site level components control the navigation and layout of any space that uses the global theme, although they can be overridden at the space and page level. (Spaces can always apply their own brand, and still retain the global layout and menu defined in these Site Settings.)
Accessing Site Settings
Accessing Space Settings
Restrict Access to Settings
To control who can change these settings: