This achievement is for playing 10 distinct songs while in co-op mode. You can select co-op mode when you pick a song and are choosing which dancer you want to be, there's a "Press X to turn on co-op mode".
The big difference in In co-op mode instead of separate scores for each player, there's a single score shared for all.
Note that for co-op mode to be available:
A) the song has to have at least two dancers (duet, trio, etc)
B) there has to be two physical players
As such you need a buddy to do this. You might be able to swing multiple players if you have multiple phones and are playing via mobile device, though even if you got multiple players that way, I'm not sure how you'd pull off Superstar on the song (as you'd have to dance simultaneously two parts with two devices).
The scoring doesn't matter for this achievement, you just need to complete each song with at least 2 players with co-op mode on. And just to be clear: it has to be 10 *different* songs, you can't just play Baby Shark 10 times in a row. :)