It's the the nontrinitarian belief that the Father, Son and Holy Spirit are different roles of one "Unitarian" God, as perceived by the believer(like a guy who's a son, a husband and a father, but still one person) rather than three distinct persons eternally existing within the One Godhead.
Tsk. Heresy.
I actually went ahead and listened to 1:40. Consider yourself Rick Rolled for subjecting me to that drek.