From b2evolution manual

This feature is available is b2evolution 3.0+

Intro posts and featured posts both appear before regular posts on skins that support this feature (typically b2evolution 3.0+). They differ in the following way:

• Featured posts are regular posts, one of which will be featured on top of the blog. That post will not be repeated in the normal flow of posts underneath. However, other/older posts with the "featured" box checked will still be displayed in the regular flow of posts.

• Intro posts are posts will a special type like "Intro-Main" or "Intro-Cat". Only one intro post will be displayed on a given view of the blog, depending on what is requested. For example, the "Intro-Main" post will apear on top of the main page of the blog. An "Intro-Cat" post will appear on top of the category pages it has been assigned to. However, no other intro post will ever be displayed in the regular flow of posts.