The InterMap is a system for defining links between WikiWikiWeb sites that was first developed by UseMod:UseModWiki and Meatball:MeatballWiki. InterMap links have the form
MapPrefix:Page, where the host prefix is converted to a partial URL based on entries in the site's intermap.txt and localmap.txt files.
The default intermap.txt distributed with PmWiki (in the scripts/ directory) includes the following InterMap entries:
Wiki: http://www.c2.com/cgi/wiki(approve sites)?
UseMod: http://www.usemod.com/cgi-bin/wiki.pl(approve sites)?
Meatball: http://www.usemod.com/cgi-bin/mb.pl(approve sites)?
Wikipedia: http://www.wikipedia.com/wiki/(approve sites)
Thus, PmWiki:Variables becomes 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/(approve sites) for Wikipedia), then do
[[Wikipedia:. | Wikipedia's main page]], which produces Wikipedia's main page. Note the . (period) after the Map: reference.