A content page works pretty much like a redirect board expect that it links to a special topic instead of an external link and uses a distinct icon in the board index. It can be used to pin important topics (like board rules or must read threads) to the board- or message index.

A content page is really just a thread that may or may not be presented with a different layout. Layouts are driven by different versions of the standard templates for presenting a topic (mainly Display.template.php and Postbit.template.php). When posting a new topic, users with sufficient permission are given the choice for selecting a non-standard thread layout and that feature works in any board - it just depends on the user's permissions.

Since these pages are actually threads, they share all functionality with normal threads but may look differently. With the blog-style layout, the first post is presented like a blog article and replies look a bit more like blog comments.

Because administrators can post html through the [html] tag they may post articles with any layout they want and the template will display such an article unmodified in its plain form.

So, it's like a blog?
Well, no, not really. It may look a bit like a single blog article with comments, but it has little to do with blogging functionality. As I already said elsewhere, a forum shouldn't try to be a blog and vice versa. Personally, I would rather aim for a bridging solution to marry the forum with a real blog instead of implementing half-baken blog functionality into a forum. For a really good blogging software, you'll need some (at least basic) CMS functionality and this goes imho too far for a forum software.