Pages on the FlightGear wiki are grouped into different namespaces. Pages in different namespaces have different uses. Pages in some namespaces interact with other pages in special ways.
Namespaces are indicated in the article name prefix, for example Help:Contents.
Pages in the main, or article namespace do not have a prefix.
The main namespace contain the articles on the wiki.
Generally images used to illustrate the wiki.
Contains the category pages which lists all the pages in a category, in essence all the pages with the same category tag, for example
[[Category:Help]]. These are linked together in a somewhat hierarchical fashion.
Templates that are used when the wiki editors either want content to be presented in a consistent manner or to lessen the amount of typing needed for common things like repository links etc.
User pages where users can present themselves, have to-do lists, sandbox pages etc.
Help pages like the one you are reading now.
These are pages with various tools, lists and statistics.
These pages contain some of the wiki's settings.
These are used for discussions about the wiki, individual pages and with users.