Using Includes
You can include the content of one page in another page by typing the following right into the editor:
[[include:SomePage]]
Just replace "SomePage" here with the name of the page you want to include.
The most common use of includes is to reuse a piece of content in several places on your site. When you edit the included page, it will automatically update in all of the pages that include it.
If a user visits a page that they can see, but it includes a page they don't have access to view, the include will not display. This provides a convenient method for having sections of content that only display to authorized users, but within the context of content that everyone can see.
You can also use includes to place Javascripts that are managed in plain text edited pages into the content of a page that uses the rich text editor.
As with Inserting Links, you can force an include tag to display as it is instead of getting processed as an include by using a ~ character, like this: [[~include:IgnoreThis]]. When you save the page, the ~ will not display.
Including Scripted Pages
Scripted pages can be included using the same method, and support the additional capability of arguments. Any characters following the page name (separated by a space) will be made available to the included scripted page as an implicit object named "include_args". For example, to set include_args in a scripted page named TestScript to "Hello world!", you would use the following: [[include:TestScript Hello world!]]. Scripted pages can use this data any way they like.