From Textpattern CMS User Documentation
Namespaces are kinda like sections. Each page can only belong to one namespace. The namespace is indicated by a word before the page title, for example "Project:Introduction" is in the "Project" namespace.
The main namespace is special in that it has no prefix. So most content pages go in the main namespace.
These are the real namespaces - all pages in these namespaces automatically have talk pages created for them too. So for example each Project page will also have an associated Project talk page.
- Main namespace - created by default.
- Project/meta namespace - here it's called "TextBook International". Usually "meta" type information is written in project namespace pages.
- User namespace - each registered user (and even anonymous IP editors, if they are allowed to edit) has an associated user page. Users can use these to display information about themselves like a profile, their interests, languages they speak, etc. User talk pages are used to communicate with other users - to leave someone a message, edit their talk page. When they next log in to the wiki, they will receive notfication of a new message to be read.
- Template namespace - similar to forms in Textpattern; see below for more info about templates.
- Category namespace - similar to categories in Textpattern; see below for more info about categories.
- Image namespace - files uploaded via Special:Upload automatically get an image page associated with them. Typically this page can be used to describe the license/author/purpose of the file. (Note even documents like PDFs will get an "image" page, if they are allowed to be uploaded. It's just a MediaWiki quirk.) See below for more on images.
- MediaWiki namespace - only administrators can edit these pages. These pages control the interface/system messages, like the menu items and names on tabs and buttons. Unless you want to tweak the interface you'll never need to know about these.
- Special namespace - Special pages have auto-generated content. For example Special:Recentchanges shows you recent activity on the site. Special:Mycontributions is where you can look at edits you've made (if you're logged in). Special:Allpages lists all the pages in the wiki. Look at Special pages to see a list of all the special pages available.
- Media namespace - see below under images.
These are all the namespaces that are created by default. It's possible to add more, e.g. "Help". If you create a page with a name like "Magic:Introduction", that doesn't automatically create a namespace called "Magic". The namespace has to be created first.