Our friend, the Octopus

Here's the table of contents for the Wikipedia article on everyone's favourite alien intelligence, the Octopus:

From Wikipedia (Source)

Based on what we've learned, what can we say about this list?

Vertical, horizontal, or matrix?

Ordered or unordered?

How many levels in the hierarchy?

What are the list items? (This is a slightly tricky question!)

How much detail is in each list item?

It's a vertical list.
It's ordered, but the sequence isn't rigid like a recipe. The list runs from from narrow—the word "Octopus"—to increasingly wide—e.g. evolution, relationship to humans. But you could change the order with minimal impact.
It has 2 levels. Notice how several categories don't have subcategories at all.
The list items are topics. Some of the topics contain their own lists, not mentioned in this table of contents.
Each list item is brief, usually 1-2 words.

You can see how these properties are shared by many of contents lists on Wikipedia, and elsewhere.

For example, here's the content list for an article on the animated series, The Owl House:

From Wikipedia (Source)

How is the Owl House contents list similar and different to the Octopus contents list?

Lists & hierarchies