Trios are one of the modes in the series. They debuted as classic routines on Just Dance 2015, but have appeared as alternate routines (On-Stage Mode) on Just Dance 2014. The mode later appeared in later games.
When selecting dancers, the lead dancer will have two spots available and the backup dancers will each have one spot available. Starting with Just Dance 2016, all three dancers can each hold the maximum possible players. That feature is only the case with eighth generation consoles and further (Xbox One, PlayStation 4, and Wii U) and the PC (which is an applicable platform starting with Just Dance 2017).
Just Dance 2016 has the most Trios out of all games with eleven (including alternate routines and Mashups) and twelve if Just Dance Unlimited is included.