Wikipedia:Tutorial (Namespaces)
In addition to the articles and their Talk pages, there are some other categories of behind-the-scenes pages that help Wikipedians communicate with each other, and serve a variety of other roles in building Wikipedia. These different areas are often referred to as namespaces — as in, "the Talk namespace".
Some other areas
Pages in the Wikipedia namespace (also known as the "Project namespace") provide information about Wikipedia and how to use it. The MediaWiki namespace contains interface texts such as link labels (What links here, etc.) and server messages. All the pages in both these areas also have corresponding MediaWiki talk pages.
Content written in a Template page will be displayed in articles that contain the corresponding template reference. For example, the content written in Template:Protected will appear in any article that contains the {{protected}} tag. Take a look at Wikipedia:Template messages to see what templates have already been created. You can use the corresponding tags in articles. You can also create new templates.
For more information on namespaces, see Wikipedia:Namespace.
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