For convenience, pages often have a "back" button to return to the previous page. This effectively turns the directed network into an undirected one. It works best when each page has exactly one "parent" page which links to it. If you can get to the same page from more than one direction, which way should the back button go? The obvious answer is to just use more than one back button.
Most websites tend toward a tree structure. There's a home page, which links to several specific pages, which may each link to several specific pages themselves. It's similar to a file/directory structure. Trees are useful because they mimic properties of sets, sorting things into categories and subcategories and so on. Though, they aren't very good at handling overlap between categories.
For convenience, we can take it for granted that each page links home, which simplifies the diagram:
When there's lots of categorical overlap, something like a tagging system may be better. This really just means that each page can have more than one incoming link. (You'll need multiple back buttons, one for each category you're in.)
Webcomics (Or webstories, more broadly) tend to have a linear structure. Page 1 links to page 2. Page 2 links to page 3. And so on, with back buttons. (It's a special case of a tree, by the way, where each parent page has exactly 1 child.) This is fitting, because stories take place over time, and time is linear. I should also mention that webcomics tend to also link every page to the beginning and end. They may also have an index, which links to every page (each page may link back to it, as well). Ignoring home/index links to simplify:
Simplifying further:
Sometimes, though, you want a story to branch into multiple "possible" paths, as in a choose-your-own-adventure story. In this case, you use a more general tree structure, with each page linking to several other pages. CYOA's also tend to link dead-ends back to the most recent "branch", so that readers can go back and explore all possible paths.
Here's another version, for quizzes.
You may also want these different paths to eventually recombine. This is especially useful for stories following multiple threads simultaneously.
This is no longer a tree. I don't know if it has a name.
There are some special stories where the end connects back to the beginning. In most mediums, this is only implied. For example, a movie might end with a repeat of the first scene, implying that the story loops. With webcomics, however, this can be fully realized.
I haven't seen many nonlinear webcomics, but it seems like there's lots of interesting possibilities. Like, what about a lattice?
I have no idea what this would be useful for. Maybe nothing. I'm interested in exploring the idea for it's own sake, though. It might be more fit for "exploring a space", as opposed to "telling a story".
What if I just... drop all restrictions. Any page can link to any other page.
Now, we're exploring a chaotic, spaghetti network. This gives me Yume Nikki vibes. It'd be easy to get lost.
Here's one shaped kinda like a dog.
I don't know if there's a point to all this. I think it's kinda interesting, though.