Magic words are words surrounded by brackets or underscores which most often insert or display the current value of what they are called. These include parser functions, variables and behavior switches and are features of wikitext. They are interpreted by the Metawiki software and are often used in templates so that they show different information depending on which page they are on and many other conditions.
There are three types of magic words:
((PAGENAME))and function somewhat similarly to templates.
For a more detailed explanation, refer to the behavior switches MediaWiki page.
__NOTOC__(can be placed anywhere in the wikitext; prevents a table of contents)
__FORCETOC__(can be placed anywhere in the wikitext; makes a table of contents appear in its normal position)
__TOC__(places a table of contents at its position)
__NOEDITSECTION__(hides section edit links beside headings)
__NEWSECTIONLINK__(adds a "+" or "new section" link for adding a new section on a non-talk page)
__NONEWSECTIONLINK__(removes the "+" or "new section" link on "Talk" pages)
__NOGALLERY__(on category pages, replaces thumbnails with normal links)
__HIDDENCAT__(on category pages, makes it a hidden category)
__INDEX__(tells search engines to index the page (show in results))
__NOINDEX__(tells search engines not to index the page (not show in results))
For documentation, you may wish to read the variables MediaWiki page.
((PAGENAME))(page title without namespace)
((BASEPAGENAME))(the page title without the current subpage or namespace — the parent page without the namespace.)
((SUBPAGENAME))(subpage part of title)
((SUBJECTPAGENAME))(associated non-talk page)
((TALKPAGENAME))(associated talk page)
((NAMESPACE))(namespace of current page)
((SUBJECTSPACE)), ((ARTICLESPACE))(associated non-talk namespace)
((TALKSPACE))(associated talk namespace)
((FULLPAGENAMEE)), ((NAMESPACEE))etc. (URL-encoded equivalents)
For more detailed information on all magic words (behaviour switches, variables and parser functions), consider reading: