Static pages are a special type of page that can be embedded within other pages / areas. 'Static Pages' is actually a really crappy name that I will eventually get around to changing as it is not an intuitive description.
When you create a static page you assign it a name - if you then include a variable of the same name in a template file or content body the variable will be replaced with the information contained in the database for the Static Page. The banner / footer and left / right columns are examples of static pages
Example
Create a static page called 'banner_advert' - Add some content to it and then save it.
Now edit the banner and add a variable called 'banner_advert' like this; [var]banner_advert[/var] - don't forget to click the save button.
Now when you view the page the banner will have the information from the 'banner_advert' Static Page in it.