Wikipedia:Why do we have outlines in addition to...?

See also Rationale for outlines.

Occasionally, an editor will notice that outlines sometimes overlap in scope and function with another type of page, and wonder why we have both. In general, it is because outlines are optimized for browsing and for showing a subject's structure. And because readers vary in their learning styles: some readers find outlines more convenient for exploring and for review than other forms of knowledge access and presentation. For more information about redundancy between Wikipedia's info navigation systems, and its benefits, see WP:CLN.

Getting back to the question, Why do we have outlines in addition to...

...subject articles?

On Wikipedia, outlines are not just regular articles. They act like a table of contents or a map for a particular topic. They help you find your way around and understand how all the different parts of a subject fit together.

Outlines are a special kind of list that helps you understand things better and faster. They are different from regular articles in the following ways:

1. Outlines are easier to read: Articles have long paragraphs of text. In outlines, you can quickly scan through the points without getting lost.
2. Outlines are better organized: The points in an outline are arranged in a neat and organized way, like branches on a tree. This makes it easy to see how different ideas are connected.
3. Outlines cover more: Outlines can cover a whole topic without missing anything important. Regular articles sometimes leave out parts because they have to be shorter.
4. Links are better in an outline: Links in an outline are all listed together in a nice, organized way. In regular articles, the links are scattered inside paragraphs all over the place, which can be confusing.

So, in short, outlines are super-organized lists that make it easier to learn about and explore different topics. They help you see the big picture and find what you need quickly!

...portals?

Outlines and portals are two different ways of organizing information on Wikipedia.

Portals are harder to make and keep up-to-date than outlines.

Outlines show up when you search Wikipedia, which is important because we want people to be able to find them easily. Portals don't show up in searches by default, and when they are included, their subpage entries make the search results very hard to read (because their many subpages clutter the results).

Outlines are big lists that cover everything about a topic. They are kind of like a table of contents for an entire subject. For example, the "Outline of Science" lists all the different branches of science like physics, chemistry, biology, etc. Outlines let you browse through an entire topic from start to finish.

Portals are like little doorways or gateways into a topic. They give you a small taste of a subject by showing you a few interesting articles related to it. Portals are kind of like the front page of a magazine, where they highlight a few articles to get you interested in reading more.

Portals are good for sampling a topic, but outlines are better if you want to survey the whole subject.

In short, we need both because they serve different purposes!

...categories?

Note: Like other types of lists on Wikipedia, outlines should never be deleted in favor of categories or navigation templates. For more information see Wikipedia:Categories, lists, and navigation templates.

On Wikipedia, we have different ways to organize information. Categories are like folders that group similar articles together. Outlines are detailed lists that show all the topics within a subject.

Outlines have some great advantages over just using categories:

1. Outlines are searchable: When you search Wikipedia, outlines show up in the results, but the lists inside categories don't.

2. With outlines, you see more: Categories use a web directory interface that show 2 levels of a subject at a time. Outlines try to show the entire subject on a single page, and so it is easier to get a sense for the whole subject.

3. Outlines are easier to browse: Outlines show all the sub-topics on one page, so you can easily scroll through them. With categories, you have to keep clicking links to go deeper, and then backtrack to drill down in the other branches. This is much slower, and you can get lost or distracted.

5. In outlines, you can show future topics: Outlines can list topics that don't have articles yet, helping us know what to work on next.

6. From an outline, you can create new articles: If a topic on an outline doesn't have an article, you can click the red link to start a new one.

7. Outlines can include details: Outlines can have descriptions, pictures, and other information alongside the topics. Categories just have a list of links.

8. Outlines allow tracking changes: We can see the edit history of outlines, so we know when topics are added or removed. Categories can't provide this for their subcategory and topics listings. Outlines work fine on watch lists. Category entries are invisible to watching.

9. Outlines are easier to edit: Outlines can be edited directly, making it faster to update them. Changing categories requires editing each article individually.

10. Outlines can become featured lists: Featured pages represent the very best Wikipedia has to offer. There is no such thing as a featured category.

So while categories are great for grouping topics, outlines give us a more detailed and flexible way to organize information within a subject. That's why we need both on Wikipedia.

...indexes?

Indexes on Wikipedia generally present articles in alphabetical order. Outlines present them as a hierarchy, showing the "familial" (parent-offspring-sibling) relationships between them, which is useful for finding and browsing subjects closely related to each other.

Indexes are comprehensive in scope and are intended to include all of the topics on a subject. Outlines by definition should include only essential links, and because of this they don't get watered down by several hundred types of cuisine or 10,000 person or place names – links to lists of these suffice in outlines, which makes outlines easier to browse.

For example, the article index for Japan has grown to be 23 pages long:

Alphabetical index: 0–9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

But if you want to see at a glance the structure of Japan as a subject, you might find the Outline of Japan more useful.

The difference between an outline and index on Wikipedia is the same as the difference between the table of contents and index of a book.