It basically enables users to organize in blocks (pages or other displays) their content - lists of any type of articles, news, comments... anything that users need. It makes extracting and retrieving content from the database very easy - it has any possible options for such purposes and is highly customizable.
For example, a user may decide to have a block on the website, containing list of the 5 most recent comments, posted to blog articles only; and the list itself may be further customized to show the date of the comment and the first sentence of the text (for example).
There's nothing that does quite the same thing as that - that's bordering on a page builder and not really the direction CMSMS aims for.
That said, a lot of similar functionality could be done with LISE, CGContentUtilities, template inheritance, and judicious use of Smarty. You have quite a bit of power to give the content editor options, but it's not an "out of the box" solution.