How does helicopters turn?

Answer 1

Generally through the combination of Roll & Yaw.

Yaw axis is similar to how a car turns, on a Copter, the tail rotor either increase or decreases its thrust, which pushes the tail in one direction, the nose in another.

Roll axis is when the entire vehicle rolls to the left or right (one side drops, while the other rises). Say one is rolling to the right: the main rotor will cause a stronger lift on the left side of the rotary wing's arc. This will cause the left side to rise, while the right side lowers.

The control unit for doing this, called the Cyclic, will have the wings increase life by increasing the angle of attack just at the point where the effect will result in life on the left side. Due to gyroscopic progression, the actual force for this is applied 90' PRIOR to where it is needed.

Generally, aircraft like to combine both Roll & Yaw to perform what is called a Coordinated turn. Trying to simply roll, or only yaw will result in a very sloppy turn. The exception to this is when a helicopter is hovering: If they wish to point the nose in another direction, using just the YAW input is perfectly justified.