when you use ailerons to turn..the down wing looses some lift....the aircraft starts to descend and (sprial) turn to the down wing..this is why you need the elevator to compensate for the loss of lift keeping the nose level.....now the elevator will bring the nose around as said above in high angle of bank turns..if you add elevator (pitch) the nose goes up... imagine the airplane hanging by one wing, where you can see the whole top of the plane..using the elevator to pitch the nose to you you just aided the turn.....
Rudder will (yaw) the plane left and right...what happens is the fuselage will partially block airflow over the wing in the direction of the yaw..(yaw left, block airflow over the left wing)...left wing looses lift..the airplane will begin to descend and turn to the left...you need elevator to keep the nose level etc etc....the difference between rudder and ailerons is you need very little rudder to loose lift on the wing...so the airplane wants to roll on you..compensate by using opposite aileron to rudder...this how you do a flat or skidding turn....depending on the airplane, you may always need opposite aileron to rudder for a good turn...now the coordinated turn is using all three axis to make turn.....believe it or not not all full scale aircraft use rudder at all times to turn....the 727 doesn't and the time I got to fly the 777 sim I was told not to use rudder
Good Flyin to all