What does it mean to say "if n"?

What does it mean to say if n? I don't get why if n works in an if statement. Shouldn't there be an argument such as if n == 0 or something, not just if n?

def AddMusicAtPosition(self, newMusic, n):
    if n:
        self.nextMusic.AddMusicAtPosition(newMusic, n - 1)
    else:
        newMusic.nextMusic = self.nextMusic
        self.nextMusic = newMusic