In this case, someone who made a playlist. Reputation of the knowledge and tastes of the playlist maker would normally matter, but since this is purely a numbers game at this point the only thing that matters is the number of followers on the list made. "Curator" makes a list of popular songs, gets a bunch of followers on the playlist, then sells placement on the list. "Curator" has really lost it's meaning here.
Collecting, selecting and presenting something. Like art in a gallery
To expand on this - a museum is just a pile of stuff without a curator who selects and organizes it to tell a cohesive story - a well curated exhibit is a wonder.