After a 30-day promotional effort, Justin Bieber's new single arrived last Friday. He performed it live for the first time at Sunday's VMAs, and then brought the track to The Tonight Show yesterday. "What Do You Mean" is feather-light, combining the buoyancy of radio hits like OMI's "Cheerleader" and Major Lazer's "Lean On" with an aching piano-ballad core. The Roots served as Bieber's adept backing band, and Black Thought burst onto stage in the middle of the song to deliver some quick, tightly-wound rhymes: That's a negative, like a pessimist/ you say it ain't love, I say yes it is! Watch above, and get to know Poo Bear, who helped Bieber write the track.