Wikipedia contains a staggering volume and remarkable variety of content, ranging from traditional encyclopedic subjects to articles about popular culture and technical topics.
Even so, every Wikipedia article must meet several criteria related to the site's mission. The most important criteria are the three core policies: Verifiability (V), No Original Research (NOR), and Neutral Point of View (NPOV). A number of further guidelines and corollaries to the major policies, particularly the notability guideline, help define what you should find in Wikipedia and what types of articles are acceptable.
Although there are now over two million articles in the English-language Wikipedia, there are even more pages devoted to the administration and community of the site. These pages, none of which are part of the Wikipedia encyclopedia, include discussion (or talk) pages; user and user talk pages; policy, procedure, and help pages; project administration and community discussion pages; image description pages; and MediaWiki-generated special site-related pages. All of these different kinds of pages are differentiated from each other by namespaces, which are indicated with prefixes that are separated from the page's name with a colon. Articles reside in the main or article namespace and have no special prefix.
In the next chapter, we'll discuss the origins of Wikipedia and how three disparate historical strands—wikis, encyclopedias, and free software—came together to influence the site's development. Skip to Chapter 3 to explore the structure of Wikipedia and learn better ways to search and browse the site or to Chapter 4 to learn how to evaluate an individual article.