This can be referred to as either the Centre of Gravity position which ensures the aircraft is balanced and within its operating limits with weight loading. It could also speak of maintaining sufficient rudder inputs to ensure that the aircraft is flying with the least amount of drag. This can be seen on the Turn and Slip Indicator by looking at the balance ball and ensuring that it is in the middle. If it is off to one side, sufficient rudder needs to be applied and held to keep the ball centred. To help remember which rudder input to use, the saying goes “Step on the ball”. If the ball is off to the right of centre, apply the right rudder. If it is off to the left, apply the left rudder.