On the left of this image, you can see the class browser; it gives you a quick overview of all classes in your project, and their methods and attributes. By clicking on them you can easily jump to the declaration or find all occurences of a particular item.
In the code view, the tooltip shows an example of KDevelop's list content type support: by analyzing your code, it is found that the highlighted variable is a dictionary which has integers as keys and further dictionaries as values.