Help:Link

The following types of hyperlink can be distinguished:

internal link in internal link style
interwiki link in internal link style
link in external link style

If no link label is specified, 1 and 2 are of the form ''target'' (with in case 2 target starting with a prefix) and 3 is of the form target or [ target ], where target is the URL including "http://". In case 3 no blank space is allowed in the URL. For MediaWiki pages the blank space can be replaced by an underscore, in general also %20 can be used; see also URLs in external links.

A label can be specified with in case 1 and 2 label and in case 3 [ target label ], with a blank space in between, see Help:Piped link.

Link type 1 will be a link to the viewing page if the page exists at the time of loading or previewing of the referring page, otherwise to the edit page.

Reasons to use type 3 to link to an internal page include:

linking to the edit page of an existing page
the referring page is a template and the link target contains a template parameter

An example of the latter is in Template:Pd: although internal link style can be used for a calculation, e.g. google:200/7, external link style like http://www.google.com/search?q=200/7 is needed when parameters are used; it is what we get with {{pd|200|7}}:

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Help:Link

See also