Carousel from Wikipedia:
A carousel (from French carrousel, from Italian carosello), or merry-go-round, is an amusement ride consisting of a rotating circular platform with seats for riders.
I don’t think they’re referring to that sort of carousel though, more likely a carousel slide projector:
A carousel slide projector is a common form of slide projector, used to project slide photographs and to create slideshows.
Mad Men: Carousel
Carousel: The gallery from Dropbox for all your photos and videos.
From the Dropbox blog:
Once upon a time, photos were something you held. You kept them safe in an album or shoebox, and it was easy to relive those moments with friends and family. Today, new apps and devices have made it easier than ever to take photos, but there’s no longer a single home for all your life’s memories.We’d like you to meet Carousel: a gallery for all the photos and videos from your life. It combines the photos in your Dropbox with the photos on your phone, and automatically backs up new ones as you take them. Carousel sorts all these memories by event so you can easily travel back in time to any photo from any date. And unlike other mobile galleries, the size of your Carousel isn’t constrained by the space on your phone, which means you can finally have your entire life’s memories in one place.