And interwiki link is one that exists between wiki site that have been administered to support one another (mutually or excluseivly).

We currently support the following sites.

{! ! Tag ! Site |- ! en | http://en.wikipedia.org/wiki/ |- |}

One can access an interwiki site using an internal link like...

[[:en:Page Name]] which translates to
http://en.wikipedia.org/wiki/Page Name

A real example is en:fair use.