The diagrams and text have been "borrowed" from the Australian Control Line Aeromodelling website.

A control line model aeroplane is one that is tethered by fine wires or cables (the lines) so that it is forced to fly in a circle. It is fitted with an elevator that can be manipulated by a pilot holding a control handle attached to the ends of the lines in the centre of the flying circle.

(Diagram from Aeromodeller Data Book published by Model & Allied Publications)

Aerobatic control line models are usually fitted with large wing flaps which move in the opposite directions to the elevators:

(Diagram from Aeromodeller Data Book published by Model & Allied Publications)