 What kinds of information can be published on Wikipedia? This is John. John wants to write a Wikipedia article about the beginning of the universe. He knows that the popular encyclopedia is the work of thousands of volunteer authors. Everyone can contribute. But what does that mean for John's article? Many people have many opinions. Political and religious topics often lead to conflict. To make sure that Wikipedia's content is trustworthy, all articles are written from a neutral point of view. Because John knows how many discussions there are about this topic, he lists various theories about it. To guarantee neutrality, he doesn't indicate which one he believes and which ones he rejects. John stays neutral so that each reader can form their own opinion. To uphold the credibility of Wikipedia and his article, John shows everyone exactly where his knowledge comes from. So, if he writes that his neighbor Anna has been on the moon, he needs to prove that with a good source. Good sources include respected technical books, academic publications, or well-researched press articles. Online sources can be used as well, of course, but especially in that case, the source must be trustworthy. For that reason, John doesn't rely on Anna's personal blog, where she presumably doesn't report on events from a neutral point of view. Also, John doesn't cite any other Wikipedia articles in his own Wikipedia article because, well, it's a vicious circle. Also, John links to his sources for everyone who wants to read more about the topic. Also, that way every reader can decide for themselves how reliable the source is. By the way, facts that are widely established, such as that the earth is round, okay, and oblate spheroid, don't require citations from John.