Aerodynamically an aircraft had three main controls, elevator, ailerons and rudder which in turn control pitch, roll and yaw. The point or rotation is around the point of balance of the aircraft.

Pitch is up and down movement, roll is obvious and yaw is best imagined as an aircraft 'skidding' sideways ie pointing in a different direction to the line of flight, but with the wings level.

Full size pilots use rudder a lot to balance maneuvers, unbalanced maneuvers are uncomfortable for the passengers.

Rudder can be used in model flying for the same thing to make the aircraft behave more realistically (as well as for some aerobatics), however for training purposes you don't need to use it other than to steer the aircraft on the ground. Get used to flying the plane accurately and safely and start experimenting with rudder when you get into your 'solo' phase.

Simon.