I had an invitation to participate in one of these a couple weeks ao and had no idea what it was. Createdbylaurie sent this explanation which help tremendously...hope it helps you!
Etsy has BNRs "Buy and Replace" and also BNS "Buy and Stay" Basically it starts out with a treasury featuring stores participating, and as people browse it other shops can purchase anything from any of the stores featured, and once they do they can take that stores place and feature something of their own as shoppers continue to browse. If you participate it helps bring traffic in your store and leads to shoppers favoriting your items/shop to also return later. If you use Google Analytics (I reccomend if you dont!) you can see how much traffic is brought in and the average time shoppers spend at your shop. I participated in some after a friend introduced me to some and decided to host my own. Each one has different rules, With mine there is no minimum to buy and I stay open all day to help get the most traffic for everyone, on my profile you can see the previous treasuries, there have been 3 rounds so far. the views are between 900 and just over 1,000 for them. I will be opening again tomorrow if you would like i can send you the link when we open for the new page, that way you can stop by and take a look to see how it goes. I carry over everyone over until they make a sale.
By the way, I did make my sale and was happy with the traffic the BNR gave me. Good luck!
Lauren@Sugartreecreek