I've been lucky enough in my short time at Etsy to have been featured in several Treasuries. Etsy Treasuries are made by fans and supporters of Etsy as a way to create a favorites page that is published and available for everyone to browse. It's a great way to visually take in a sampling of what Etsy has to offer. Treasuries can be grouped by themes, colors, interests, materials, almost anything! Some are quite artfully done and reflect a real curatorial bent. Quite often Etsy team members will build Treasuries to showcase their team. I've been in several Treasuries just because of my team memberships in EtsyFAST, EtsyDallas, and Etsy Texas Crafters.
There is also a secondary treasury called Treasury West. It is labeled the experimental treasury and can disappear at any time. Treasuries are competitive and very much like a game. The more clicks you get on a Treasury the higher that list goes on the master list.If popular enough, it might even be selected as the front page of Etsy. Understandably, Treasuries are sought after and the space is limited. Even if you want to make one, there might not be room! So, there is much excitement if one is able to "score" a Treasury and then there is a frenzy to get the word out so you get lots of unique clicks and your list will be bumped up.
Each Treasury has an expiration date. Some would-be Treasury creators will troll the list looking for almost expired lists so they can time their attempt. The title of the list itself is also important and tends to be clever and not always descriptive. The point is to make you look, even if what you find surprises you. On the whole, I find Treasuries a pleasant diversion and fun way to browse. I'm always thrilled when I find myself in one; there is a small yellow star next to the name of the list when one of your own items is included, if you're logged in.