A namespace is name, an identifier at a higher level.
This page is in the name space 'Help'. You can see its name space in the tab at the top left of this page, it reads: "Help page" In this namespace all pages are grouped which provide help text.
Te purpose of using several namespaces lies in the possibility to use one and the same identifier several times without creating any ambiguity. The identifier WikiIndex can be used in several namespaces:
- In the Main namespace (the 'unnamed' namespace) WikiIndex is the wiki page that is on the same level as all other wiki pages that are entries to this wiki-index. It tells how it came into being, who founded it, where it is, how big it is and the like.
- In the namespace Help Help:WikiIndex is the root page for all help pages about this wiki.
The use of namespaces requires a technical concept that supports namespace which, of course, is already implemented in the MediaWiki software. And in the frame of this concept it requires the explicit definition of any namespace one desires, except the main namespace which is the namespace that would be available even without the concept of having several namespaces. Such definition is ready made in the software packet for most basic pages like File Pages or can be done by a sysop for project specific namespaces like WikiIndex Pages on this wiki.