Google acquired the streaming music service Songza more than a year ago, and it has operated in parallel with Google Play Music all this time. But no more. Songza is being shuttered on January 31st, so existing users have about two months to migrate over to Play Music. The good news, most of Songza's features are already in Play Music.
Google certainly wasted no time making use of the technology and expertise is got from Songza. Play Music has all the contextual radio stations and curated playlists of Songza already. Google also decided to make those stations free recently, so even those without a Play Music sub can listen (with ads). That should make the end of Songza less painful for users. Although, the Songza team is really pushing the narrative that Songza and Play Music are becoming one product.
Songza users are getting emails about the change, and will be able to migrate their accounts to Google smoothly. Playlists, favorites, and even thumbs-ups will be transferred. You can keep using Songza for the time being, but its days are numbered.