Infosphere:Citation
Citations are footnotes appearing in articles providing references to specific content inline. This article will describe how to use them on the Infosphere. When to use them, how and when not to.
Difference from Wikipedia
If you are accustomed to the policies of Wikipedia regarding 'reliable sources' and the infamous [[[wikipedia:Wikipedia:Citation needed|citation needed]]]-template, then you should know that things are first and foremost a lot different here.
The basic rule for most purposes is no citation is needed and you probably shouldn't care. So you may think the guideline should stop right here, but no, because there are certainly situations they are required or needed at best. But in most cases, it just makes the articles better.
When to use citations
First, understand what citations is for. They provide inline references to the content at hand. Be it either to a commentary or a web article, they usually back up the claims made in the article.
Secondly, put yourself in the eyes of your readers. Always imagine your reader coming to your article without any prior knowledge. So their usual reaction will not be where are their sources on this?!, but rather that's interesting, I wonder if there is more of this?.