By default, topic display categories show the category description just beneath the category's title, before displaying the content or intro article.
Now that the intro article exists, we've found it a bit redundant to have a category description AND an intro article there.
So we've added a new Display option to topic display categories so that you can choose to Hide description. (Previously, we'd suggested using a Snippet with some Custom CSS for this, which worked, but was just way too much work.)
See Topic display: Hide category description for more information!