Its two accounts that have separate libraries but are.
However, while both Spotify Duo users can listen at the same time, they will need to use the same street address in their account information in order to use the Duo plan (the same restriction applies to the Spotify, Apple Music and YouTube Music Family plans as well). So I recently discovered that spotify have now got an account for couples called Spotify Duo. Obviously, Spotify Duo isn’t just for romantic partners it could also work well for smaller families, two friends, roommates, or if you share a workspace with someone and want to go dutch on a music streaming plan for the office. There’s also a special “Duo Mix” playlist that includes tracks both users listen to in case you want to share new music with each other or have a single playlist running while doing stuff around the house. Spotify Premium duo consists of the parallel management of two users of each of their accounts, the payment is one but there are two accounts included in this.