In simple terms (before the pedants jump in!)... The tailplane is all moving on the 737 it moves in response to pitch trim. It also has a elevators which move in response to control column inputs. It also has balance tabs which are mechanically linked to the elevators and move in response to elevator movement to assist elevator movement.
Those who have availed themselves of the further reading material will be aware that the rules change during manual reversion and with flap etc but that is the advanced lesson!
I have put an extra photograph on the page you linked to showing each piece labelled.
S&L