Needs update for 1.3. Most of this is true only for classic
The header on each page allows you to go to the FrontPage (home), RecentChanges (recent modifications), TitleIndex (index of all the page titles), WordIndex (index of all the words in the page titles), SiteNavigation (list of navigation tools), and HelpContents (main help page).
On the upper right you find icons for the most often used functions:
Icon(print) shows a printable version of the page without the header or footer
Icon(raw) shows the source code of the current page
Icon(edit) allows you to say something, i.e. edit the page
Icon(info) shows meta information about the page, especially the full version history
Icon(diff) shows changes between the current version and the previous version of the page
Icon(find) shows the search page.
Icon(help) shows the help page
Clicking on the Page Title link located in the header above will show every page that references this page. A sample use of this back-referencing, inverted-links feature is the categorization of pages, i.e. CategoryHomepage. On the bottom of each page, you find the "traditional" edit and search links known from the original wiki, and in addition fields for quick-searching titles and the page texts, plus links to call any custom actions you have installed.