There are two types of general topics lists: Outlines and Indexes. Outlines are arranged hierarchically, while the topics in indexes are presented alphabetically.
The vast majority of lists on Wikipedia present the items of a class of things – those are item lists. The rest are general topics lists which are different than item lists because they present the subtopics of a given subject – their scope is an entire subject.
For example, for sharks, the item list is List of sharks and it presents shark species. A general topics list on sharks is the Outline of sharks, and its scope is everything about sharks.