The InterMap is a system for defining links between WikiWikiWeb sites that was first developed by UseMod:UseModWiki and Meatball:MeatballWiki. The method is to use a word that stands for a path that is defined. InterMap links have the form
MapPrefix:PagePath, where the host prefix is converted to a partial URL based on entries in the site's intermap.txt and localmap.txt files.
Thus, "PmWiki:Variables" becomes "http://www.pmwiki.org/wiki/PmWiki/" + "Variables," a link to the PmWiki.Variables page on the official PmWiki web site, Wiki:FrontPage is a link to the front page of the first WikiWikiWeb, and Wikipedia:Stonehenge takes you to the Wikipedia article about the famous megaliths in England.
Like other links, you can use the double-bracket syntax to get different link text:
[[Meatball:StartingPoints | starting points]] over at Meatballbecomes "starting points over at Meatball"
[[starting points -> Meatball:StartingPoints]] over at Meatballbecomes "starting points over at Meatball"
If you want to link just to what the intermap says (e.g. http://www.wikipedia.com/wiki/ for Wikipedia), then do
[[Wikipedia:. | Wikipedia's main page]], which produces Wikipedia's main page. Note the . (period) after the Map: reference.