Ramapriya wrote:

... why does the banking of wings by the use of ailerons not just
roll an aircraft but also produces a turn (yaw)?

Simply stated, when an aircraft is in level flight, the lift of the
wings works directly against gravity. When an aircraft rolls one
direction or the other, the lift of the wings rolls away from vertical,
remaining at 90 degrees to the wings. This means only part of the lift
works against gravity. The rest causes the aircraft to swing away from
straight flight. It is somewhat akin to the effect of banking on a race
track.