This is the compiled version of the XML outline. The structure table is maintained automatically. It's updated when you edit the XML outline. There's also an optional table named globals which is discussed further below. The top level item is named siteTree.
Sites can contain other sites.
It also has an address item pointing to the website itself. This address is a string that can be coerced to a Frontier address. Serving from the file system Instead of an address, a site can have a folderPath. This way you can serve a site that's been statically rendered to the file system. Items in this table are added to the page table, in the responder attributes sub-table.