→ Feature Name
Pools are publicly editable (wiki-like) Galleries that show special navigation bar in image page of each image.
Feature parity with danbooru-like boorus. Feature is aimed towards comic artists and comic uploaders, so they could upload without having to manually link pages in the description.
Pools are for comics, image series, and other sequential art. They provide easy navigation between pages, and a highly visible index. Pools are NOT aimed for collection of subjectively picked art, we have Galleries for that.
Pools can be created by anyone, and edited by anyone.
Pools contain images, in specific order (that can be rearranged by anyone).
Each image page of image that's added to the pool will have navigation panel displayed:
[first prev PoolName next last]
Each of those are links. First and Last links to first and last image in the pool. Prev and Next links to previous and next image, relative to current image (pool order apply). PoolName is Pool's title and links to pool page containing ordered list of all images.
One image can be in multiple pools (but it's best to limit max number of pools per image to 2-4, to prevent panel creep).
Also, there should be public logs like in tags (image added to pool, removed from pool, pool reordered).
Why not just use Galleries as-it-is?
Because Galleries are equivalent of "Favorite Folders" from DeviantArt. They're nice, but do not allow public editing and do not display navigation panel. A new type of Gallery (Pool) need to be created.
Why not just use "series:*" or "comic:*" tags?
Pools and tags serve different purposes. Tags can't have specific order, so user can't add page between page 3 and page 4 (which happens quite often in sponsored comics, or when artist adds covers for chapters). Plus they still do not have navigation panel.
Why not just link first/prev/next/last in the description?
Poor maintainability for prev/next buttons (you have to keep track of three descriptions on three pages every time you upload), and utter impracticality for last button (you have to edit every single page). Also, description is not editable by anyone, so you're mainly stuck with it.
But Philomena already have navigation buttons back/next!
Those are not comic navigation buttons, those are search query (or global if navigated not from search page) navigation buttons. e621 also have them, separate from pool navigation panel.
But Derpibooru was fine without Pools for 8 years, why Ponybooru need them now?
Derpibooru was in unique position after closure of Ponibooru in 2012. Bronibooru's rules were too strict (no shipping, etc), and Derpibooru was the only one left. That's not the case now, so feature parity with other booru engines is important. Also, Ponybooru is rather small for now, so this is a perfect time to introduce a new feature without overwhelming moderators and assistants.
e621 and danbooru-based sites have this feature. You can use Galleries as a base for making Pools.
danbooru-based sites call Pools as "purple-colored pools", and call Galleries as "blue-colored pools". Do not confuse them.