When to use
{{Wikipediainfo}} should never be used on real world pages. It is meant for in-universe pages only.
It is not a substitute for writing an article of our own. We certainly don't want to link to wikipedia:The Dalek Invasion of Earth or wikipedia:Verity Lambert, and thereby lose our readers to wikipedia just because we haven't yet written our article as completely as we could.
Rather, it is a way to give our readers an easy link to real world information about a topic within the DWU. This allows curious readers to easily compare the real world subject with the way it was handled in the DWU. For instance Marco Polo's biographical details in the real world are substantively different than they are in the DWU. Moreover, there are many cases in the DWU where a real world subject, like Great Expectations or Bruce Springsteen, is only mentioned in passing. We therefore don't have enough information from valid sources to write more than a few sentences. {{wikipediainfo}} gives us a way to write about only what is covered in the DWU, but still give our readers quick access to the subject.
Error correction
Sometimes, the name of our articles are not precisely the same as those on Wikipedia. A proper link can be established by forcing a different spelling, so as to match an article name. For instance, we have an article called "football" on this wiki. If we were just to type
{{wikipediainfo}}
on our football page, the resulting the link would be to wikipedia:football. This isn't what we want, though, because wikipedia:football discusses all types of football, including American, Australian, Canadian and rugby. Clearly we don't want to link to that, since our article is about what's formally known as association football.
So how do we link to wikipedia:association football? Easy:
{{wikipediainfo|association football}}
Template classification
This template is deliberately classified as "unknown" so that it will show up on a variety of devices, including phones. This is different from the policy used for the similar-looking stub tags, which we class as "notice" templates.
Deprecated variable
It used to be that this template provided a text link to Wikipedia, which highlighted the name of the article. It was possible to alter the name of that highlighted link by adding a third variable. To follow on with our above example:
{{wikipediainfo|association football|football}}
Would have produced a text link that read "football" but in fact linked to wikipedia:association football.
This coding has been retained, but it now does nothing.